MNC Technical Interview Questions and Answers 2025

// Java Solution
public String reverseString(String str) {
    StringBuilder reversed = new StringBuilder();
    for (int i = str.length() - 1; i >= 0; i--) {
        reversed.append(str.charAt(i));
    }
    return reversed.toString();
}

// Time Complexity: O(n)
// Space Complexity: O(n)

// Java Solution
public int findSecondLargest(int[] arr) {
    int largest = Integer.MIN_VALUE;
    int secondLargest = Integer.MIN_VALUE;
    
    for (int num : arr) {
        if (num > largest) {
            secondLargest = largest;
            largest = num;
        } else if (num > secondLargest && num != largest) {
            secondLargest = num;
        }
    }
    return secondLargest;
}

// Time Complexity: O(n)
// Space Complexity: O(1)

// Java Solution
public ListNode reverseList(ListNode head) {
    ListNode prev = null;
    ListNode current = head;
    
    while (current != null) {
        ListNode next = current.next;
        current.next = prev;
        prev = current;
        current = next;
    }
    return prev;
}

// Time Complexity: O(n)
// Space Complexity: O(1)

// Java Solution
public boolean isBalanced(TreeNode root) {
    return checkHeight(root) != -1;
}

private int checkHeight(TreeNode node) {
    if (node == null) return 0;
    
    int leftHeight = checkHeight(node.left);
    if (leftHeight == -1) return -1;
    
    int rightHeight = checkHeight(node.right);
    if (rightHeight == -1) return -1;
    
    if (Math.abs(leftHeight - rightHeight) > 1) return -1;
    
    return Math.max(leftHeight, rightHeight) + 1;
}

// Time Complexity: O(n)
// Space Complexity: O(h) where h is height

// Java Solution
public int binarySearch(int[] arr, int target) {
    int left = 0;
    int right = arr.length - 1;
    
    while (left <= right) {
        int mid = left + (right - left) / 2;
        
        if (arr[mid] == target) {
            return mid;
        } else if (arr[mid] < target) {
            left = mid + 1;
        } else {
            right = mid - 1;
        }
    }
    return -1;
}

// Time Complexity: O(log n)
// Space Complexity: O(1)

SELECT * FROM employees 
WHERE salary > 50000
ORDER BY salary DESC;