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Give a real-world application of nested loops.

Searching for a specific pixel in an image (2D array).

How are nested loops used in game development?

To iterate through game boards or maps, checking for collisions, or updating game states.

How are nested loops used in data analysis?

To compare all pairs of data points in a dataset, calculate correlations, or identify patterns.

What does the following code output?

java
public static void printPyramid(int n) {
    for (int i = 0; i < n; i++) {
        for (int j = i; j < n; j++) {
            System.out.print("*");
        }
        System.out.println();
    }
}
printPyramid(3);

** *

What does the following code output?

java
public static void printPyramid(int n) {
    for (int i = 0; i < n; i++) {
        for (int j = i; j < n; j++) {
            System.out.print(i+j);
        }
        System.out.println();
    }
}
printPyramid(3);

012 23 4

What does the following code output?

java
public static void printPyramid(int n) {
    for (int i = 0; i < n; i++) {
        for (int j = i; j < n; j++) {
            if (i == 1 && j == 1) {
                break;
            }
            System.out.print(i+j);
        }
        System.out.println();
    }
}
printPyramid(3);

012 2 4

What does the following code output?

java
public static void printPyramid(int n) {
    for (int i = 0; i < n; i++) {
        for (int j = i; j < n; j++) {
            if (i == 1 && j == 1) {
                continue;
            }
            System.out.print(i+j);
        }
        System.out.println();
    }
}
printPyramid(3);

012 23 4

Identify the potential issue in the following code:

java
for (int i = 0; i < n; i++) {
    for (int j = 0; i < m; j++) {
        System.out.println(i + " " + j);
    }
}

The inner loop condition i < m should be j < m to avoid an infinite loop or incorrect behavior.

What will be the value of primes after the following code executes with n = 3?

java
public static ArrayList<Integer> findNPrimes(int n) {
    int prime = 2;
    ArrayList<Integer> primes = new ArrayList<Integer>();
    for (int i = 0; i < n; i++) { // Outer loop: Finds n primes
        boolean notPrime = false;
        while (!notPrime) { // Middle loop: Checks if current number is prime
            for (int j = 2; j < prime; j++){ // Inner loop: Checks for divisors
                if (prime % j == 0) {
                    notPrime = true;
                    break; // Exit inner loop if not prime
                }
            }
            if (notPrime) {
                prime++;
                notPrime = false;
            } else {
                notPrime = true; // Exit middle loop if prime
            }
        }
        primes.add(prime);
        prime++;
    }
    return primes;
}
ArrayList<Integer> primes = findNPrimes(3);

[2, 3, 5]

What is the output of the following code snippet?

java
int[][] matrix = {{1, 2, 3}, {4, 5, 6}, {7, 8, 9}};
for (int i = 0; i < matrix.length; i++) {
    for (int j = 0; j < matrix[i].length; j++) {
        if (matrix[i][j] % 2 == 0) {
            System.out.print(matrix[i][j] + " ");
        }
    }
}

2 4 6 8

What is the output of this code?

java
for (int i = 1; i <= 3; i++) {
    for (int j = 1; j <= 3; j++) {
        System.out.print(i * j + " ");
    }
    System.out.println();
}

1 2 3 2 4 6 3 6 9

What is the output of the following code?

java
int count = 0;
for (int i = 0; i < 5; i++) {
    for (int j = i + 1; j < 5; j++) {
        count++;
    }
}
System.out.println(count);

What is the output of the following code snippet?

java
int x = 0;
for (int i = 0; i < 3; i++) {
    for (int j = 0; j < 3; j++) {
        if (i == j) {
            x += i + j;
        }
    }
}
System.out.println(x);

What is the key difference between break and continue in nested loops?

break exits the loop entirely, while continue only skips the current iteration.