Free Java Interview Question And Answers Pdf [Quiz -7]

Java Interview Question And Answers Pdf ( Quiz -7 )

1. Matrix Transpose:
   Write a program or function that takes a square matrix as input and returns its transpose. The transpose of a matrix is obtained by swapping the rows and columns.

public class MatrixTranspose {
    public static int[][] transposeMatrix(int[][] matrix) {
        int rows = matrix.length;
        int columns = matrix[0].length;
        int[][] transpose = new int[columns][rows];

        for (int i = 0; i < rows; i++) {
            for (int j = 0; j < columns; j++) {
                transpose[j][i] = matrix[i][j];
            }
        }

        return transpose;
    }

    public static void main(String[] args) {
        int[][] matrix = {
            {1, 2, 3},
            {4, 5, 6},
            {7, 8, 9}
        };
        int[][] transposedMatrix = transposeMatrix(matrix);
        for (int[] row : transposedMatrix) {
            for (int element : row) {
                System.out.print(element + " ");
            }
            System.out.println();
        }
    }
}

Check 50+ JAVA Projects with Source Code

2. Remove Duplicates from an Array:
   Create a program or function that removes duplicate elements from an array and returns the array with only unique elements.

import java.util.Arrays;
import java.util.LinkedHashSet;

public class RemoveDuplicatesFromArray {
    public static int[] removeDuplicates(int[] array) {
        return Arrays.stream(array).distinct().toArray();
    }

    public static void main(String[] args) {
        int[] array = {1, 2, 3, 4, 3, 2, 5};
        int[] uniqueArray = removeDuplicates(array);
        System.out.println("Unique Array: " + Arrays.toString(uniqueArray));
    }
}

Check 100+ JAVA Spring Boot Projects with Source Code

Check for Perfect Number: Write a function to check if a given positive integer is a perfect number. A perfect number is a positive integer that is equal to the sum of its proper divisors (excluding itself).

public class PerfectNumber {
    public static boolean isPerfectNumber(int number) {
        if (number <= 1) {
            return false;
        }
        int sum = 1;
        for (int i = 2; i * i <= number; i++) {
            if (number % i == 0) {
                sum += i;
                if (i * i != number) {
                    sum += number / i;
                }
            }
        }
        return sum == number;
    }

    public static void main(String[] args) {
        int number = 28; // Example number
        System.out.println("Is Perfect Number: " + isPerfectNumber(number));
    }
}

Find Missing Number:
Write a program or function that finds the missing number in a given array of integers containing numbers from 1 to n, where n is the length of the array

public class FindMissingNumber {
    public static int findMissingNumber(int[] nums) {
        int expectedSum = nums.length * (nums.length + 1) / 2;
        int actualSum = 0;
        for (int num : nums) {
            actualSum += num;
        }
        return expectedSum - actualSum;
    }

    public static void main(String[] args) {
        int[] array = {1, 2, 4, 5, 6}; // Example array with one missing number
        System.out.println("Missing Number: " + findMissingNumber(array));
    }
}

Reverse a Linked List: Implement a function to reverse a singly linked list

class ListNode {
    int val;
    ListNode next;

    ListNode(int val) {
        this.val = val;
    }
}

public class ReverseLinkedList {
    public static ListNode reverseLinkedList(ListNode head) {
        ListNode prev = null;
        ListNode current = head;
        while (current != null) {
            ListNode nextNode = current.next;
            current.next = prev;
            prev = current;
            current = nextNode;
        }
        return prev;
    }

    public static void main(String[] args) {
        ListNode head = new ListNode(1);
        head.next = new ListNode(2);
        head.next.next = new ListNode(3);
        head.next.next.next = new ListNode(4);
        head.next.next.next.next = new ListNode(5);

        ListNode reversedList = reverseLinkedList(head);

        while (reversedList != null) {
            System.out.print(reversedList.val + " ");
            reversedList = reversedList.next;
        }
    }
}