Java程序辅导
C C++ Java Python Processing编程在线培训 程序编写 软件开发 视频讲解
C C++ Java Python Processing编程在线培训 程序编写 软件开发 视频讲解
CS 61B // Spring 2022
Introduction to Java
Discussion 02
CS 61B // Spring 2022
Announcements
1. Lab 1, Lab 2, and HW 0 due Friday 01/28 (all
of these CANNOT be dropped)
2. HW 1 released Tuesday at noon, due next
Tuesday 02/01
3. OH starts this week entirely online
4. Please complete the Pre-Semester Survey!
2
CS 61B // Spring 2022
All About Your TA!
Edit this slide to include an intro about yourself.
3
CS 61B // Spring 2022
Review
4
CS 61B // Spring 2022
Anatomy of a Function
/** Print all primes up to and including LIMIT. */
private static void printPrimes(int limit) {
for (int p = 2; p < = limit; p += 1) {
if (isPrime(p)) {
System.out.print(p + " ");
}
}
System.out.println();
}
Comments
Keywords for the basic elements of the
language (we will cover more later)
Type declarations - Java is statically
typed so we have to tell the computer
what type of value every variable holds
and what every function returns
Variable and Function Names that allow
us to refer to our stored values
Don’t forget the brackets and
semicolons!
5
CS 61B // Spring 2022
Structure of a Class
public class CS61BStudent { // Class Declaration
public int idNumber; // Instance Variables
public int grade;
public static String professor = “Hilfinger”; // Class (Static) Variables
public CS61BStudent (int id) { // Constructor
this.idNumber = id;
this.grade = 100;
}
public void watchLecture() { // Instance Method
...
}
public static void updateGrades() { // Class (Static) Method
...
}
}
6
CS 61B // Spring 2022
Instantiating Classes
public class CS61BLauncher {
public static void main(String[] args) {
CS61BStudent studentOne; // Declare class
studentOne = new CS61BStudent(32259); // Instantiate and assign class
CS61BStudent studentTwo = new CS61BStudent(19234); // Both at once
studentOne.watchLecture(); // Instance methods are called on instance
CS61BStudent.updateGrades(); // Static methods can be
// called by class OR instance
}
}
7
CS 61B // Spring 2022
Static vs. Instance
Static variables and functions belong to the whole class.
Example: Every 61B Student shares the same professor, and if the professor were to change it would change for
everyone.
Instance variables and functions belong to each individual instance.
Example: Each 61B Student has their own ID number, and changing a student’s ID number doesn’t change
anything for any other student.
8
CS 61B // Spring 2022
Worksheet
9
CS 61B // Spring 2022
1 Old Town Code
1 int x = 7;
2 String chorus = “Thank u, next”;
3 Singer queen = new Singer(“Ariana”);
4
5 while (x > 0) {
6 x -= 1;
7 queen.sing(chorus);
8 }
9
10 String[] phrases = {“love”, “patience”, “pain”, “what does the fox say?”};
11
12 for (int i = 0; i < 3; i += 1) {
13 System.out.println(“One taught me “ + phrases[i]);
14 }
15
16 System.out.println(phrases[phrases.length - 1]);
What does this output?
10
CS 61B // Spring 2022
1 Old Town Code
1 int x = 7; // Declares var x and assigns 7 to it
2 String chorus = “Thank u, next”;
3 Singer queen = new Singer(“Ariana”);
4
5 while (x > 0) {
6 x -= 1;
7 queen.sing(chorus);
8 }
9
10 String[] phrases = {“love”, “patience”, “pain”, “what does the fox say?”};
11
12 for (int i = 0; i < 3; i += 1) {
13 System.out.println(“One taught me “ + phrases[i]);
14 }
15
16 System.out.println(phrases[phrases.length - 1]);
What does this output?
11
CS 61B // Spring 2022
1 Old Town Code
1 int x = 7; // Declares var x and assigns 7 to it
2 String chorus = “Thank u, next”; // Declares var chorus and assigns a String to it
3 Singer queen = new Singer(“Ariana”);
4
5 while (x > 0) {
6 x -= 1;
7 queen.sing(chorus);
8 }
9
10 String[] phrases = {“love”, “patience”, “pain”, “what does the fox say?”};
11
12 for (int i = 0; i < 3; i += 1) {
13 System.out.println(“One taught me “ + phrases[i]);
14 }
15
16 System.out.println(phrases[phrases.length - 1]);
What does this output?
12
CS 61B // Spring 2022
1 Old Town Code
1 int x = 7; // Declares var x and assigns 7 to it
2 String chorus = “Thank u, next”; // Declares var chorus and assigns a String to it
3 Singer queen = new Singer(“Ariana”); // Declares var queen and assigns a Singer to it
4
5 while (x > 0) {
6 x -= 1;
7 queen.sing(chorus);
8 }
9
10 String[] phrases = {“love”, “patience”, “pain”, “what does the fox say?”};
11
12 for (int i = 0; i < 3; i += 1) {
13 System.out.println(“One taught me “ + phrases[i]);
14 }
15
16 System.out.println(phrases[phrases.length - 1]);
What does this output?
13
CS 61B // Spring 2022
1 Old Town Code
1 int x = 7; // Declares var x and assigns 7 to it
2 String chorus = “Thank u, next”; // Declares var chorus and assigns a String to it
3 Singer queen = new Singer(“Ariana”); // Declares var queen and assigns a Singer to it
4
5 while (x > 0) { // Checks if x is still greater than 0
6 x -= 1; // If so it deducts 1 from x
7 queen.sing(chorus); // And it calls the queen.sing method on chorus
8 }
9
10 String[] phrases = {“love”, “patience”, “pain”, “what does the fox say?”};
11
12 for (int i = 0; i < 3; i += 1) {
13 System.out.println(“One taught me “ + phrases[i]);
14 }
15
16 System.out.println(phrases[phrases.length - 1]);
What does this output?
14
CS 61B // Spring 2022
1 Old Town Code
1 int x = 7; // Declares var x and assigns 7 to it
2 String chorus = “Thank u, next”; // Declares var chorus and assigns a String to it
3 Singer queen = new Singer(“Ariana”); // Declares var queen and assigns a Singer to it
4
5 while (x > 0) { // Checks if x is still greater than 0
6 x -= 1; // If so it deducts 1 from x
7 queen.sing(chorus); // And it calls the queen.sing method on chorus
8 }
9
10 String[] phrases = {“love”, “patience”, “pain”, “what does the fox say?”};
11 // Declares var phrases and assigns an array of Strings to it
12 for (int i = 0; i < 3; i += 1) {
13 System.out.println(“One taught me “ + phrases[i]);
14 }
15
16 System.out.println(phrases[phrases.length - 1]);
What does this output?
15
CS 61B // Spring 2022
1 Old Town Code
1 int x = 7; // Declares var x and assigns 7 to it
2 String chorus = “Thank u, next”; // Declares var chorus and assigns a String to it
3 Singer queen = new Singer(“Ariana”); // Declares var queen and assigns a Singer to it
4
5 while (x > 0) { // Checks if x is still greater than 0
6 x -= 1; // If so it deducts 1 from x
7 queen.sing(chorus); // And it calls the queen.sing method on chorus
8 }
9
10 String[] phrases = {“love”, “patience”, “pain”, “what does the fox say?”};
11 // Declares var phrases and assigns an array of Strings to it
12 for (int i = 0; i < 3; i += 1) { // Declares i and checks if its still less than 3
13 System.out.println(“One taught me “ + phrases[i]); // If so it prints
14 } // And increments by one
15
16 System.out.println(phrases[phrases.length - 1]);
What does this output?
16
CS 61B // Spring 2022
1 Old Town Code
1 int x = 7; // Declares var x and assigns 7 to it
2 String chorus = “Thank u, next”; // Declares var chorus and assigns a String to it
3 Singer queen = new Singer(“Ariana”); // Declares var queen and assigns a Singer to it
4
5 while (x > 0) { // Checks if x is still greater than 0
6 x -= 1; // If so it deducts 1 from x
7 queen.sing(chorus); // And it calls the queen.sing method on chorus
8 }
9
10 String[] phrases = {“love”, “patience”, “pain”, “what does the fox say?”};
11 // Declares var phrases and assigns an array of Strings to it
12 for (int i = 0; i < 3; i += 1) { // Declares i and checks if its still less than 3
13 System.out.println(“One taught me “ + phrases[i]); // If so it prints
14 } // And increments by one
15
16 System.out.println(phrases[phrases.length - 1]); // Prints the last phrase in phrases
What does this output?
17
CS 61B // Spring 2022
1 Old Town Code
1 int x = 7;
2 String chorus = “Thank u, next”;
3 Singer queen = new Singer(“Ariana”);
4
5 while (x > 0) {
6 x -= 1;
7 queen.sing(chorus);
8 }
9
10 String[] phrases = {“love”, “patience”, “pain”, “what does the fox say?”};
11
12 for (int i = 0; i < 3; i += 1) {
13 System.out.println(“One taught me “ + phrases[i]);
14 }
15
16 System.out.println(phrases[phrases.length - 1]);
Console Output
One taught me love
One taught me patience
One taught me pain
What does the fox say?
What does this output?
18
CS 61B // Spring 2022
2 Reading Code: A Mystery
1 public static int mystery1(int[] inputArray, int k) {
2 int x = inputArray[k];
3 int answer = k;
4 int index = k + 1;
5 while (index < inputArray.length) {
6 if (inputArray[index] < x) {
7 x = inputArray[index];
8 answer = index;
9 }
10 index = index + 1;
11 }
12 return answer;
13 }
What does this return when the input array is [3, 0, 4, 6, 3] and k is 2?
What does this answer mean?
19
CS 61B // Spring 2022
2 Reading Code: A Mystery
1 public static int mystery1(int[] inputArray, int k) {
2 int x = inputArray[k];
3 int answer = k;
4 int index = k + 1;
5 while (index < inputArray.length) {
6 if (inputArray[index] < x) {
7 x = inputArray[index];
8 answer = index;
9 }
10 index = index + 1;
11 }
12 return answer;
13 }
What does this return when the input array is [3, 0, 4, 6, 3] and k is 2?
What does this answer mean?
20
3 0 4 6 3
2
inputArray
k
CS 61B // Spring 2022
2 Reading Code: A Mystery
1 public static int mystery1(int[] inputArray, int k) {
2 int x = inputArray[k];
3 int answer = k;
4 int index = k + 1;
5 while (index < inputArray.length) {
6 if (inputArray[index] < x) {
7 x = inputArray[index];
8 answer = index;
9 }
10 index = index + 1;
11 }
12 return answer;
13 }
What does this return when the input array is [3, 0, 4, 6, 3] and k is 2?
What does this answer mean?
21
3 0 4 6 3
2
inputArray
k
4x
CS 61B // Spring 2022
2 Reading Code: A Mystery
1 public static int mystery1(int[] inputArray, int k) {
2 int x = inputArray[k];
3 int answer = k;
4 int index = k + 1;
5 while (index < inputArray.length) {
6 if (inputArray[index] < x) {
7 x = inputArray[index];
8 answer = index;
9 }
10 index = index + 1;
11 }
12 return answer;
13 }
What does this return when the input array is [3, 0, 4, 6, 3] and k is 2?
What does this answer mean?
22
3 0 4 6 3
2
inputArray
k
4x
2answer
CS 61B // Spring 2022
2 Reading Code: A Mystery
1 public static int mystery1(int[] inputArray, int k) {
2 int x = inputArray[k];
3 int answer = k;
4 int index = k + 1;
5 while (index < inputArray.length) {
6 if (inputArray[index] < x) {
7 x = inputArray[index];
8 answer = index;
9 }
10 index = index + 1;
11 }
12 return answer;
13 }
What does this return when the input array is [3, 0, 4, 6, 3] and k is 2?
What does this answer mean?
23
3 0 4 6 3
2
inputArray
k
4x
2answer
3index
CS 61B // Spring 2022
2 Reading Code: A Mystery
1 public static int mystery1(int[] inputArray, int k) {
2 int x = inputArray[k];
3 int answer = k;
4 int index = k + 1;
5 while (index < inputArray.length) { // True
6 if (inputArray[index] < x) {
7 x = inputArray[index];
8 answer = index;
9 }
10 index = index + 1;
11 }
12 return answer;
13 }
What does this return when the input array is [3, 0, 4, 6, 3] and k is 2?
What does this answer mean?
24
3 0 4 6 3
2
inputArray
k
4x
2answer
3index
CS 61B // Spring 2022
2 Reading Code: A Mystery
1 public static int mystery1(int[] inputArray, int k) {
2 int x = inputArray[k];
3 int answer = k;
4 int index = k + 1;
5 while (index < inputArray.length) {
6 if (inputArray[index] < x) { // False
7 x = inputArray[index];
8 answer = index;
9 }
10 index = index + 1;
11 }
12 return answer;
13 }
What does this return when the input array is [3, 0, 4, 6, 3] and k is 2?
What does this answer mean?
25
3 0 4 6 3
2
inputArray
k
4x
2answer
3index
CS 61B // Spring 2022
2 Reading Code: A Mystery
1 public static int mystery1(int[] inputArray, int k) {
2 int x = inputArray[k];
3 int answer = k;
4 int index = k + 1;
5 while (index < inputArray.length) {
6 if (inputArray[index] < x) {
7 x = inputArray[index]; // Skip this line
8 answer = index; // and this one
9 }
10 index = index + 1;
11 }
12 return answer;
13 }
What does this return when the input array is [3, 0, 4, 6, 3] and k is 2?
What does this answer mean?
26
3 0 4 6 3
2
inputArray
k
4x
2answer
3index
CS 61B // Spring 2022
2 Reading Code: A Mystery
1 public static int mystery1(int[] inputArray, int k) {
2 int x = inputArray[k];
3 int answer = k;
4 int index = k + 1;
5 while (index < inputArray.length) {
6 if (inputArray[index] < x) {
7 x = inputArray[index];
8 answer = index;
9 }
10 index = index + 1;
11 }
12 return answer;
13 }
What does this return when the input array is [3, 0, 4, 6, 3] and k is 2?
What does this answer mean?
27
3 0 4 6 3
2
inputArray
k
4x
2answer
4index
CS 61B // Spring 2022
2 Reading Code: A Mystery
1 public static int mystery1(int[] inputArray, int k) {
2 int x = inputArray[k];
3 int answer = k;
4 int index = k + 1;
5 while (index < inputArray.length) { // still True
6 if (inputArray[index] < x) {
7 x = inputArray[index];
8 answer = index;
9 }
10 index = index + 1;
11 }
12 return answer;
13 }
What does this return when the input array is [3, 0, 4, 6, 3] and k is 2?
What does this answer mean?
28
3 0 4 6 3
2
inputArray
k
4x
2answer
4index
CS 61B // Spring 2022
2 Reading Code: A Mystery
1 public static int mystery1(int[] inputArray, int k) {
2 int x = inputArray[k];
3 int answer = k;
4 int index = k + 1;
5 while (index < inputArray.length) {
6 if (inputArray[index] < x) { // True
7 x = inputArray[index];
8 answer = index;
9 }
10 index = index + 1;
11 }
12 return answer;
13 }
What does this return when the input array is [3, 0, 4, 6, 3] and k is 2?
What does this answer mean?
29
3 0 4 6 3
2
inputArray
k
4x
2answer
4index
CS 61B // Spring 2022
2 Reading Code: A Mystery
1 public static int mystery1(int[] inputArray, int k) {
2 int x = inputArray[k];
3 int answer = k;
4 int index = k + 1;
5 while (index < inputArray.length) {
6 if (inputArray[index] < x) {
7 x = inputArray[index];
8 answer = index;
9 }
10 index = index + 1;
11 }
12 return answer;
13 }
What does this return when the input array is [3, 0, 4, 6, 3] and k is 2?
What does this answer mean?
30
3 0 4 6 3
2
inputArray
k
3x
2answer
4index
CS 61B // Spring 2022
2 Reading Code: A Mystery
1 public static int mystery1(int[] inputArray, int k) {
2 int x = inputArray[k];
3 int answer = k;
4 int index = k + 1;
5 while (index < inputArray.length) {
6 if (inputArray[index] < x) {
7 x = inputArray[index];
8 answer = index;
9 }
10 index = index + 1;
11 }
12 return answer;
13 }
What does this return when the input array is [3, 0, 4, 6, 3] and k is 2?
What does this answer mean?
31
3 0 4 6 3
2
inputArray
k
3x
4answer
4index
CS 61B // Spring 2022
2 Reading Code: A Mystery
1 public static int mystery1(int[] inputArray, int k) {
2 int x = inputArray[k];
3 int answer = k;
4 int index = k + 1;
5 while (index < inputArray.length) {
6 if (inputArray[index] < x) {
7 x = inputArray[index];
8 answer = index;
9 }
10 index = index + 1;
11 }
12 return answer;
13 }
What does this return when the input array is [3, 0, 4, 6, 3] and k is 2?
What does this answer mean?
32
3 0 4 6 3
2
inputArray
k
3x
4answer
5index
CS 61B // Spring 2022
2 Reading Code: A Mystery
1 public static int mystery1(int[] inputArray, int k) {
2 int x = inputArray[k];
3 int answer = k;
4 int index = k + 1;
5 while (index < inputArray.length) { // False
6 if (inputArray[index] < x) {
7 x = inputArray[index];
8 answer = index;
9 }
10 index = index + 1;
11 }
12 return answer;
13 }
What does this return when the input array is [3, 0, 4, 6, 3] and k is 2?
What does this answer mean?
33
3 0 4 6 3
2
inputArray
k
3x
4answer
5index
CS 61B // Spring 2022
2 Reading Code: A Mystery
1 public static int mystery1(int[] inputArray, int k) {
2 int x = inputArray[k];
3 int answer = k;
4 int index = k + 1;
5 while (index < inputArray.length) {
6 if (inputArray[index] < x) { // Skip
7 x = inputArray[index]; // all
8 answer = index; // of
9 } // these
10 index = index + 1; // lines
11 }
12 return answer;
13 }
What does this return when the input array is [3, 0, 4, 6, 3] and k is 2?
What does this answer mean?
34
3 0 4 6 3
2
inputArray
k
3x
4answer
5index
CS 61B // Spring 2022
2 Reading Code: A Mystery
1 public static int mystery1(int[] inputArray, int k) {
2 int x = inputArray[k];
3 int answer = k;
4 int index = k + 1;
5 while (index < inputArray.length) {
6 if (inputArray[index] < x) {
7 x = inputArray[index];
8 answer = index;
9 }
10 index = index + 1;
11 }
12 return answer;
13 }
What does this return when the input array is [3, 0, 4, 6, 3] and k is 2?
What does this answer mean?
Return: 4
The returned value is the index of
the smallest value in the array
that occurs at or after index k.
35
CS 61B // Spring 2022
2 Reading Code: A Mystery Extra
1 public static void mystery2(int[] inputArray) {
2 int index = 0;
3 while (index < inputArray.length) {
4 int targetIndex = mystery1(inputArray, index);
5 int temp = inputArray[targetIndex];
6 inputarray[targetIndex] = inputArray[index];
7 inputArray[index] = temp;
8 index = index + 1;
9 }
10 }
What does this return when the input array is [3, 0, 4, 6, 3]?
What does this function do?
36
CS 61B // Spring 2022
2 Reading Code: A Mystery Extra
1 public static void mystery2(int[] inputArray) {
2 int index = 0;
3 while (index < inputArray.length) {
4 int targetIndex = mystery1(inputArray, index);
5 int temp = inputArray[targetIndex];
6 inputarray[targetIndex] = inputArray[index];
7 inputArray[index] = temp;
8 index = index + 1;
9 }
10 }
What does this return when the input array is [3, 0, 4, 6, 3]?
What does this function do?
37
3 0 4 6 3inputArray
CS 61B // Spring 2022
2 Reading Code: A Mystery Extra
1 public static void mystery2(int[] inputArray) {
2 int index = 0;
3 while (index < inputArray.length) {
4 int targetIndex = mystery1(inputArray, index);
5 int temp = inputArray[targetIndex];
6 inputarray[targetIndex] = inputArray[index];
7 inputArray[index] = temp;
8 index = index + 1;
9 }
10 }
What does this return when the input array is [3, 0, 4, 6, 3]?
What does this function do?
38
3 0 4 6 3inputArray
0index
CS 61B // Spring 2022
2 Reading Code: A Mystery Extra
1 public static void mystery2(int[] inputArray) {
2 int index = 0;
3 while (index < inputArray.length) { // True
4 int targetIndex = mystery1(inputArray, index);
5 int temp = inputArray[targetIndex];
6 inputarray[targetIndex] = inputArray[index];
7 inputArray[index] = temp;
8 index = index + 1;
9 }
10 }
What does this return when the input array is [3, 0, 4, 6, 3]?
What does this function do?
39
3 0 4 6 3inputArray
0index
CS 61B // Spring 2022
2 Reading Code: A Mystery Extra
1 public static void mystery2(int[] inputArray) {
2 int index = 0;
3 while (index < inputArray.length) {
4 int targetIndex = mystery1(inputArray, index);
5 int temp = inputArray[targetIndex];
6 inputarray[targetIndex] = inputArray[index];
7 inputArray[index] = temp;
8 index = index + 1;
9 }
10 }
What does this return when the input array is [3, 0, 4, 6, 3]?
What does this function do?
40
3 0 4 6 3inputArray
0index
1targetIndex
CS 61B // Spring 2022
2 Reading Code: A Mystery Extra
1 public static void mystery2(int[] inputArray) {
2 int index = 0;
3 while (index < inputArray.length) {
4 int targetIndex = mystery1(inputArray, index);
5 int temp = inputArray[targetIndex];
6 inputarray[targetIndex] = inputArray[index];
7 inputArray[index] = temp;
8 index = index + 1;
9 }
10 }
What does this return when the input array is [3, 0, 4, 6, 3]?
What does this function do?
41
3 0 4 6 3inputArray
0index
1targetIndex
0temp
CS 61B // Spring 2022
2 Reading Code: A Mystery Extra
1 public static void mystery2(int[] inputArray) {
2 int index = 0;
3 while (index < inputArray.length) {
4 int targetIndex = mystery1(inputArray, index);
5 int temp = inputArray[targetIndex];
6 inputarray[targetIndex] = inputArray[index];
7 inputArray[index] = temp;
8 index = index + 1;
9 }
10 }
What does this return when the input array is [3, 0, 4, 6, 3]?
What does this function do?
42
3 3 4 6 3inputArray
0index
1targetIndex
0temp
CS 61B // Spring 2022
2 Reading Code: A Mystery Extra
1 public static void mystery2(int[] inputArray) {
2 int index = 0;
3 while (index < inputArray.length) {
4 int targetIndex = mystery1(inputArray, index);
5 int temp = inputArray[targetIndex];
6 inputarray[targetIndex] = inputArray[index];
7 inputArray[index] = temp;
8 index = index + 1;
9 }
10 }
What does this return when the input array is [3, 0, 4, 6, 3]?
What does this function do?
43
0 3 4 6 3inputArray
0index
1targetIndex
0temp
CS 61B // Spring 2022
2 Reading Code: A Mystery Extra
1 public static void mystery2(int[] inputArray) {
2 int index = 0;
3 while (index < inputArray.length) {
4 int targetIndex = mystery1(inputArray, index);
5 int temp = inputArray[targetIndex];
6 inputarray[targetIndex] = inputArray[index];
7 inputArray[index] = temp;
8 index = index + 1;
9 }
10 }
What does this return when the input array is [3, 0, 4, 6, 3]?
What does this function do?
44
0 3 4 6 3inputArray
1index
1targetIndex
0temp
CS 61B // Spring 2022
2 Reading Code: A Mystery Extra
1 public static void mystery2(int[] inputArray) {
2 int index = 0;
3 while (index < inputArray.length) { // True
4 int targetIndex = mystery1(inputArray, index);
5 int temp = inputArray[targetIndex];
6 inputarray[targetIndex] = inputArray[index];
7 inputArray[index] = temp;
8 index = index + 1;
9 }
10 }
What does this return when the input array is [3, 0, 4, 6, 3]?
What does this function do?
45
0 3 4 6 3inputArray
1index
1targetIndex
0temp
CS 61B // Spring 2022
2 Reading Code: A Mystery Extra
1 public static void mystery2(int[] inputArray) {
2 int index = 0;
3 while (index < inputArray.length) {
4 int targetIndex = mystery1(inputArray, index);
5 int temp = inputArray[targetIndex];
6 inputarray[targetIndex] = inputArray[index];
7 inputArray[index] = temp;
8 index = index + 1;
9 }
10 }
What does this return when the input array is [3, 0, 4, 6, 3]?
What does this function do?
46
0 3 4 6 3inputArray
1index
1targetIndex
0temp
CS 61B // Spring 2022
2 Reading Code: A Mystery Extra
1 public static void mystery2(int[] inputArray) {
2 int index = 0;
3 while (index < inputArray.length) {
4 int targetIndex = mystery1(inputArray, index);
5 int temp = inputArray[targetIndex];
6 inputarray[targetIndex] = inputArray[index];
7 inputArray[index] = temp;
8 index = index + 1;
9 }
10 }
What does this return when the input array is [3, 0, 4, 6, 3]?
What does this function do?
47
0 3 4 6 3inputArray
1index
1targetIndex
1temp
CS 61B // Spring 2022
2 Reading Code: A Mystery Extra
1 public static void mystery2(int[] inputArray) {
2 int index = 0;
3 while (index < inputArray.length) {
4 int targetIndex = mystery1(inputArray, index);
5 int temp = inputArray[targetIndex];
6 inputarray[targetIndex] = inputArray[index];
7 inputArray[index] = temp;
8 index = index + 1;
9 }
10 }
What does this return when the input array is [3, 0, 4, 6, 3]?
What does this function do?
48
0 3 4 6 3inputArray
1index
1targetIndex
1temp
CS 61B // Spring 2022
2 Reading Code: A Mystery Extra
1 public static void mystery2(int[] inputArray) {
2 int index = 0;
3 while (index < inputArray.length) {
4 int targetIndex = mystery1(inputArray, index);
5 int temp = inputArray[targetIndex];
6 inputarray[targetIndex] = inputArray[index];
7 inputArray[index] = temp;
8 index = index + 1;
9 }
10 }
What does this return when the input array is [3, 0, 4, 6, 3]?
What does this function do?
49
0 3 4 6 3inputArray
1index
1targetIndex
1temp
CS 61B // Spring 2022
2 Reading Code: A Mystery Extra
1 public static void mystery2(int[] inputArray) {
2 int index = 0;
3 while (index < inputArray.length) {
4 int targetIndex = mystery1(inputArray, index);
5 int temp = inputArray[targetIndex];
6 inputarray[targetIndex] = inputArray[index];
7 inputArray[index] = temp;
8 index = index + 1;
9 }
10 }
What does this return when the input array is [3, 0, 4, 6, 3]?
What does this function do?
50
0 3 4 6 3inputArray
2index
1targetIndex
1temp
CS 61B // Spring 2022
2 Reading Code: A Mystery Extra
1 public static void mystery2(int[] inputArray) {
2 int index = 0;
3 while (index < inputArray.length) { // True
4 int targetIndex = mystery1(inputArray, index);
5 int temp = inputArray[targetIndex];
6 inputarray[targetIndex] = inputArray[index];
7 inputArray[index] = temp;
8 index = index + 1;
9 }
10 }
What does this return when the input array is [3, 0, 4, 6, 3]?
What does this function do?
51
0 3 4 6 3inputArray
2index
1targetIndex
1temp
CS 61B // Spring 2022
2 Reading Code: A Mystery Extra
1 public static void mystery2(int[] inputArray) {
2 int index = 0;
3 while (index < inputArray.length) {
4 int targetIndex = mystery1(inputArray, index);
5 int temp = inputArray[targetIndex];
6 inputarray[targetIndex] = inputArray[index];
7 inputArray[index] = temp;
8 index = index + 1;
9 }
10 }
What does this return when the input array is [3, 0, 4, 6, 3]?
What does this function do?
52
0 3 4 6 3inputArray
2index
4targetIndex
1temp
CS 61B // Spring 2022
2 Reading Code: A Mystery Extra
1 public static void mystery2(int[] inputArray) {
2 int index = 0;
3 while (index < inputArray.length) {
4 int targetIndex = mystery1(inputArray, index);
5 int temp = inputArray[targetIndex];
6 inputarray[targetIndex] = inputArray[index];
7 inputArray[index] = temp;
8 index = index + 1;
9 }
10 }
What does this return when the input array is [3, 0, 4, 6, 3]?
What does this function do?
53
0 3 4 6 3inputArray
2index
4targetIndex
3temp
CS 61B // Spring 2022
2 Reading Code: A Mystery Extra
1 public static void mystery2(int[] inputArray) {
2 int index = 0;
3 while (index < inputArray.length) {
4 int targetIndex = mystery1(inputArray, index);
5 int temp = inputArray[targetIndex];
6 inputarray[targetIndex] = inputArray[index];
7 inputArray[index] = temp;
8 index = index + 1;
9 }
10 }
What does this return when the input array is [3, 0, 4, 6, 3]?
What does this function do?
54
0 3 4 6 4inputArray
2index
4targetIndex
3temp
CS 61B // Spring 2022
2 Reading Code: A Mystery Extra
1 public static void mystery2(int[] inputArray) {
2 int index = 0;
3 while (index < inputArray.length) {
4 int targetIndex = mystery1(inputArray, index);
5 int temp = inputArray[targetIndex];
6 inputarray[targetIndex] = inputArray[index];
7 inputArray[index] = temp;
8 index = index + 1;
9 }
10 }
What does this return when the input array is [3, 0, 4, 6, 3]?
What does this function do?
55
0 3 3 6 4inputArray
2index
4targetIndex
3temp
CS 61B // Spring 2022
2 Reading Code: A Mystery Extra
1 public static void mystery2(int[] inputArray) {
2 int index = 0;
3 while (index < inputArray.length) {
4 int targetIndex = mystery1(inputArray, index);
5 int temp = inputArray[targetIndex];
6 inputarray[targetIndex] = inputArray[index];
7 inputArray[index] = temp;
8 index = index + 1;
9 }
10 }
What does this return when the input array is [3, 0, 4, 6, 3]?
What does this function do?
56
0 3 3 6 4inputArray
3index
4targetIndex
3temp
CS 61B // Spring 2022
2 Reading Code: A Mystery Extra
1 public static void mystery2(int[] inputArray) {
2 int index = 0;
3 while (index < inputArray.length) { // True
4 int targetIndex = mystery1(inputArray, index);
5 int temp = inputArray[targetIndex];
6 inputarray[targetIndex] = inputArray[index];
7 inputArray[index] = temp;
8 index = index + 1;
9 }
10 }
What does this return when the input array is [3, 0, 4, 6, 3]?
What does this function do?
57
0 3 3 6 4inputArray
3index
4targetIndex
3temp
CS 61B // Spring 2022
2 Reading Code: A Mystery Extra
1 public static void mystery2(int[] inputArray) {
2 int index = 0;
3 while (index < inputArray.length) {
4 int targetIndex = mystery1(inputArray, index);
5 int temp = inputArray[targetIndex];
6 inputarray[targetIndex] = inputArray[index];
7 inputArray[index] = temp;
8 index = index + 1;
9 }
10 }
What does this return when the input array is [3, 0, 4, 6, 3]?
What does this function do?
58
0 3 3 6 4inputArray
3index
4targetIndex
3temp
CS 61B // Spring 2022
2 Reading Code: A Mystery Extra
1 public static void mystery2(int[] inputArray) {
2 int index = 0;
3 while (index < inputArray.length) {
4 int targetIndex = mystery1(inputArray, index);
5 int temp = inputArray[targetIndex];
6 inputarray[targetIndex] = inputArray[index];
7 inputArray[index] = temp;
8 index = index + 1;
9 }
10 }
What does this return when the input array is [3, 0, 4, 6, 3]?
What does this function do?
59
0 3 3 6 4inputArray
3index
4targetIndex
4temp
CS 61B // Spring 2022
2 Reading Code: A Mystery Extra
1 public static void mystery2(int[] inputArray) {
2 int index = 0;
3 while (index < inputArray.length) {
4 int targetIndex = mystery1(inputArray, index);
5 int temp = inputArray[targetIndex];
6 inputarray[targetIndex] = inputArray[index];
7 inputArray[index] = temp;
8 index = index + 1;
9 }
10 }
What does this return when the input array is [3, 0, 4, 6, 3]?
What does this function do?
60
0 3 3 6 6inputArray
3index
4targetIndex
4temp
CS 61B // Spring 2022
2 Reading Code: A Mystery Extra
1 public static void mystery2(int[] inputArray) {
2 int index = 0;
3 while (index < inputArray.length) {
4 int targetIndex = mystery1(inputArray, index);
5 int temp = inputArray[targetIndex];
6 inputarray[targetIndex] = inputArray[index];
7 inputArray[index] = temp;
8 index = index + 1;
9 }
10 }
What does this return when the input array is [3, 0, 4, 6, 3]?
What does this function do?
61
0 3 3 4 6inputArray
3index
4targetIndex
4temp
CS 61B // Spring 2022
2 Reading Code: A Mystery Extra
1 public static void mystery2(int[] inputArray) {
2 int index = 0;
3 while (index < inputArray.length) {
4 int targetIndex = mystery1(inputArray, index);
5 int temp = inputArray[targetIndex];
6 inputarray[targetIndex] = inputArray[index];
7 inputArray[index] = temp;
8 index = index + 1;
9 }
10 }
What does this return when the input array is [3, 0, 4, 6, 3]?
What does this function do?
62
0 3 3 4 6inputArray
4index
4targetIndex
4temp
CS 61B // Spring 2022
2 Reading Code: A Mystery Extra
1 public static void mystery2(int[] inputArray) {
2 int index = 0;
3 while (index < inputArray.length) { // True
4 int targetIndex = mystery1(inputArray, index);
5 int temp = inputArray[targetIndex];
6 inputarray[targetIndex] = inputArray[index];
7 inputArray[index] = temp;
8 index = index + 1;
9 }
10 }
What does this return when the input array is [3, 0, 4, 6, 3]?
What does this function do?
63
0 3 3 4 6inputArray
4index
4targetIndex
4temp
CS 61B // Spring 2022
2 Reading Code: A Mystery Extra
1 public static void mystery2(int[] inputArray) {
2 int index = 0;
3 while (index < inputArray.length) {
4 int targetIndex = mystery1(inputArray, index);
5 int temp = inputArray[targetIndex];
6 inputarray[targetIndex] = inputArray[index];
7 inputArray[index] = temp;
8 index = index + 1;
9 }
10 }
What does this return when the input array is [3, 0, 4, 6, 3]?
What does this function do?
64
0 3 3 4 6inputArray
4index
4targetIndex
4temp
CS 61B // Spring 2022
2 Reading Code: A Mystery Extra
1 public static void mystery2(int[] inputArray) {
2 int index = 0;
3 while (index < inputArray.length) {
4 int targetIndex = mystery1(inputArray, index);
5 int temp = inputArray[targetIndex];
6 inputarray[targetIndex] = inputArray[index];
7 inputArray[index] = temp;
8 index = index + 1;
9 }
10 }
What does this return when the input array is [3, 0, 4, 6, 3]?
What does this function do?
65
0 3 3 4 6inputArray
4index
4targetIndex
6temp
CS 61B // Spring 2022
2 Reading Code: A Mystery Extra
1 public static void mystery2(int[] inputArray) {
2 int index = 0;
3 while (index < inputArray.length) {
4 int targetIndex = mystery1(inputArray, index);
5 int temp = inputArray[targetIndex];
6 inputarray[targetIndex] = inputArray[index];
7 inputArray[index] = temp;
8 index = index + 1;
9 }
10 }
What does this return when the input array is [3, 0, 4, 6, 3]?
What does this function do?
66
0 3 3 4 6inputArray
4index
4targetIndex
6temp
CS 61B // Spring 2022
2 Reading Code: A Mystery Extra
1 public static void mystery2(int[] inputArray) {
2 int index = 0;
3 while (index < inputArray.length) {
4 int targetIndex = mystery1(inputArray, index);
5 int temp = inputArray[targetIndex];
6 inputarray[targetIndex] = inputArray[index];
7 inputArray[index] = temp;
8 index = index + 1;
9 }
10 }
What does this return when the input array is [3, 0, 4, 6, 3]?
What does this function do?
67
0 3 3 4 6inputArray
4index
4targetIndex
6temp
CS 61B // Spring 2022
2 Reading Code: A Mystery Extra
1 public static void mystery2(int[] inputArray) {
2 int index = 0;
3 while (index < inputArray.length) {
4 int targetIndex = mystery1(inputArray, index);
5 int temp = inputArray[targetIndex];
6 inputarray[targetIndex] = inputArray[index];
7 inputArray[index] = temp;
8 index = index + 1;
9 }
10 }
What does this return when the input array is [3, 0, 4, 6, 3]?
What does this function do?
68
0 3 3 4 6inputArray
5index
4targetIndex
6temp
CS 61B // Spring 2022
2 Reading Code: A Mystery Extra
1 public static void mystery2(int[] inputArray) {
2 int index = 0;
3 while (index < inputArray.length) { // False
4 int targetIndex = mystery1(inputArray, index);
5 int temp = inputArray[targetIndex];
6 inputarray[targetIndex] = inputArray[index];
7 inputArray[index] = temp;
8 index = index + 1;
9 }
10 }
What does this return when the input array is [3, 0, 4, 6, 3]?
What does this function do?
69
0 3 3 4 6inputArray
5index
4targetIndex
6temp
CS 61B // Spring 2022
2 Reading Code: A Mystery Extra
1 public static void mystery2(int[] inputArray) {
2 int index = 0;
3 while (index < inputArray.length) { // False
4 int targetIndex = mystery1(inputArray, index);
5 int temp = inputArray[targetIndex];
6 inputarray[targetIndex] = inputArray[index];
7 inputArray[index] = temp;
8 index = index + 1;
9 }
10 }
What does this return when the input array is [3, 0, 4, 6, 3]?
What does this function do?
70
0 3 3 4 6inputArray
5index
4targetIndex
6temp
CS 61B // Spring 2022
2 Reading Code: A Mystery Extra
1 public static void mystery2(int[] inputArray) {
2 int index = 0;
3 while (index < inputArray.length) {
4 int targetIndex = mystery1(inputArray, index);
5 int temp = inputArray[targetIndex];
6 inputarray[targetIndex] = inputArray[index];
7 inputArray[index] = temp;
8 index = index + 1;
9 }
10 }
What does this return when the input array is [3, 0, 4, 6, 3]?
What does this function do?
Return: Nothing (return type is void)
This function sorts the array in increasing order in place, so
our input array turns into [0, 3, 3, 4, 6]
71
CS 61B // Spring 2022
3 Recursion Practice: Fibonacci
Implement a function fib1 that recursively calculates the Nth fibonacci number.
Hint: fib(N) = fib(N-1) + fib(N-2)
public static int fib1(int N) {
}
72
CS 61B // Spring 2022
3 Recursion Practice: Fibonacci
Implement a function fib1 that recursively calculates the Nth fibonacci number.
Hint: fib(N) = fib(N-1) + fib(N-2)
public static int fib1(int N) {
if (N <= 1) { // Base case - can be written a few different ways
return N;
}
}
73
CS 61B // Spring 2022
3 Recursion Practice: Fibonacci
Implement a function fib1 that recursively calculates the Nth fibonacci number.
Hint: fib(N) = fib(N-1) + fib(N-2)
public static int fib1(int N) {
if (N <= 1) {
return N;
} else {
return fib1(N - 1) + fib1(N - 2);
} // Just copying over the same recursive formula from the hint
}
74
CS 61B // Spring 2022
3 Recursion Practice: Fibonacci Extra
Implement a function fib2 that recursively calculates the Nth fibonacci number more efficiently with new
arguments k, f0, and f1 in 5 lines or less.
Hint: To compute the Nth fibonacci number, call fib2(N, 0, 0 1)
public static int fib2(int N, int k, int f0, int f1) {
}
75
CS 61B // Spring 2022
3 Recursion Practice: Fibonacci Extra
Implement a function fib2 that recursively calculates the Nth fibonacci number more efficiently with new
arguments k, f0, and f1 in 5 lines or less.
Hint: To compute the Nth fibonacci number, call fib2(N, 0, 0 1)
public static int fib2(int N, int k, int f0, int f1) {
}
/* N = the number of recursions in the end
* k = the number recursions already accomplished (hint -> starts @ 0)
* f0 = the second to last fib num (hint -> the 0th fibonacci number (0))
* f1 = the last fib num (hint -> the 1st fibonacci number (1))
*/
76
CS 61B // Spring 2022
3 Recursion Practice: Fibonacci Extra
Implement a function fib2 that recursively calculates the Nth fibonacci number more efficiently with new
arguments k, f0, and f1 in 5 lines or less.
Hint: To compute the Nth fibonacci number, call fib2(N, 0, 0 1)
public static int fib2(int N, int k, int f0, int f1) {
if (N == k) { // num recursions goal == num recursions accomplished
return f0; // when N == k, we want f0 (ex. N == 0, we want f0 = 0)
}
}
77
CS 61B // Spring 2022
3 Recursion Practice: Fibonacci Extra
Implement a function fib2 that recursively calculates the Nth fibonacci number more efficiently with new
arguments k, f0, and f1 in 5 lines or less.
Hint: To compute the Nth fibonacci number, call fib2(N, 0, 0 1)
public static int fib2(int N, int k, int f0, int f1) {
if (N == k) {
return f0;
} else { // N stays same, k increments, f0 = f1, f1 = f1 + f2
return fib2(N, k + 1, f1, f0 + f1);
}
}
78