Top Cognizant Interview Questions

What is the difference between monolithic architecture and microservices architecture?

What are the benefits of using Agile methodology in software development?

What is the purpose of a design pattern in software development?

What is the difference between a hash table and a binary search tree?

What are the principles of object-oriented programming?

What is the purpose of a database index?

What is the difference between a left join and a right join in SQL?

What is the purpose of a load balancer in a distributed system?

What are the benefits of using a cloud-based infrastructure?

What is the difference between a public cloud and a private cloud?

What is the purpose of a firewall in a network?

What are the principles of network security?

What is the difference between a hub and a switch in a network?

What is the purpose of a router in a network?

What are the benefits of using a virtual private network (VPN)?

What is the difference between a LAN and a WAN?

What are the principles of IT service management?

What is the purpose of a configuration management system?

What are the benefits of using a version control system?

What is the difference between a bug and a defect in software development?

Write a Java function to reverse a linked list.

public class Node {
  int data;
  Node next;
  public Node(int data) {
    
    this.data = data;
    this.next = null;
  }
}
public class LinkedList {
  Node head;
  public void reverse() {
    
    Node prev = null;
    Node current = head;
    Node next = null;
    while (current != null) {
      
      next = current.next;
      current.next = prev;
      prev = current;
      current = next;
    }
    head = prev;
  }
}

Write a Python function to find the maximum value in a binary tree.

class Node: def __init__(self, data): self.data = data self.left = None self.right = None def find_max(root): if root is None: return float('-inf') else: return max(root.data, find_max(root.left), find_max(root.right))

Write a JavaScript function to sort an array of integers using the quicksort algorithm.

function quicksort(arr) {
  if (arr.length <= 1) {
    return arr;
  }
  let pivot = arr[0];
  let left = arr.slice(1).filter((x) => x <= pivot);
  let right = arr.slice(1).filter((x) => x > pivot);
  return quicksort(left).concat([pivot], quicksort(right));
}

Write a C++ function to find the first duplicate in an array of integers.

void find_first_duplicate(int arr[], int n) {
  unordered_set<int> seen;
  for (int i = 0;
  i < n;
  i++) {
    if (seen.find(arr[i]) != seen.end()) {
      cout << arr[i] << endl;
      return;
    }
    seen.insert(arr[i]);
  }
  cout << -1 << endl;
}

Write a Java function to check if a string is a palindrome.

public class Main {
  public static boolean isPalindrome(String s) {
    
    int left = 0;
    int right = s.length() - 1;
    while (left < right) {
      
      if (s.charAt(left) != s.charAt(right)) {
        
        return false;
      }
      left++;
      right--;
    }
    return true;
  }
}

Write a Python function to find the minimum value in a stack.

class Stack: def __init__(self): self.items = [] def push(self, item): self.items.append(item) def pop(self): return self.items.pop() def find_min(self): return min(self.items)

Write a JavaScript function to implement a queue using two stacks.

class Queue {
constructor() {

this.stack1 = [];
this.stack2 = [];
}
enqueue(item) {

this.stack1.push(item);
}
dequeue() {

if (this.stack2.length === 0) {

while (this.stack1.length > 0) {

this.stack2.push(this.stack1.pop());
}
}
return this.stack2.pop();
}
}

Write a C++ function to find the maximum sum of a subarray within an array of integers.

int maxSubArraySum(int arr[], int n) {
  int max_so_far = arr[0];
  int max_ending_here = arr[0];
  for (int i = 1;
  i < n;
  i++) {
    max_ending_here = max(arr[i], max_ending_here + arr[i]);
    max_so_far = max(max_so_far, max_ending_here);
  }
  return max_so_far;
}