TCS Coding Questions

About TCS National Qualifier Test (NQT)

TCS National Qualifier Test (NQT) is a standardized assessment conducted by Tata Consultancy Services for recruiting fresh graduates from various educational institutions across India. It serves as the initial screening process for entry-level roles at TCS and offers multiple career opportunities to candidates.

Test Pattern

Career Tracks Based on Performance

Based on test performance, candidates qualify for one of the following hiring categories:

• Prime : Highest tier offering - requires excellent performance in both Foundation and Advanced sections
• Digital : Advanced technical role - Advanced section is mandatory for consideration
• Ninja : Standard developer role - can qualify with strong Foundation section performance

Application Process

1. Log in to the TCS NextStep Portal
2. Register and Apply for the Drive
3. Select In-center mode of test and choose preferred test centers
4. Track application status - should reflect as "Applied for Drive"

Interview Process

After clearing the NQT, candidates undergo a rigorous interview process that includes programming questions. The complexity varies based on the role:

• Prime : Most challenging technical questions and system design concepts
• Digital : Advanced DSA topics and problem-solving skills
• Ninja : Fundamental programming concepts and basic algorithms

MOST COMMONLY GIVEN PROGRAMMING QUESTIONS IN INTERVIEW ROUND IN TCS

Check for Leap Year

function isLeapYear(year) {
  if (year % 400 === 0) return true;
  if (year % 100 === 0) return false;
  return year % 4 === 0;
}

// Example usage
console.log(isLeapYear(2020)); // true
console.log(isLeapYear(2100)); // false
console.log(isLeapYear(2000)); // true

Fibonacci Sequence

function generateFibonacci(n) {
  const fibonacci = [0, 1];

  for (let i = 2; i < n; i++) {
    fibonacci[i] = fibonacci[i-1] + fibonacci[i-2];
  }

  return fibonacci.slice(0, n);
}

// Example usage
console.log(generateFibonacci(10)); // [0, 1, 1, 2, 3, 5, 8, 13, 21, 34]

Prime Number Check

function isPrime(num) {
  if (num <= 1) return false;
  if (num <= 3) return true;

  if (num % 2 === 0 || num % 3 === 0) return false;

  let i = 5;
  while (i * i <= num) {
    if (num % i === 0 || num % (i + 2) === 0) return false;
    i += 6;
  }

  return true;
}

// Example usage
console.log(isPrime(11)); // true
console.log(isPrime(15)); // false

Sum of Natural Numbers

function sumOfNaturalNumbers(n) {
  return (n * (n + 1)) / 2;
}

// Example usage
console.log(sumOfNaturalNumbers(10)); // 55

Array Rotation

function rotateArray(arr, k) {
  const n = arr.length;
  k = k % n;

  const rotated = [...arr.slice(n - k), ...arr.slice(0, n - k)];
  return rotated;
}

// Example usage
console.log(rotateArray([1, 2, 3, 4, 5], 2)); // [4, 5, 1, 2, 3]

Find Maximum and Minimum in an Array

function findMaxMin(arr) {
  if (arr.length === 0) return { max: undefined, min: undefined };

  let max = arr[0];
  let min = arr[0];

  for (let i = 1; i < arr.length; i++) {
    if (arr[i] > max) max = arr[i];
    if (arr[i] < min) min = arr[i];
  }

  return { max, min };
}

// Example usage
console.log(findMaxMin([3, 5, 1, 9, 2])); // { max: 9, min: 1 }

Palindrome String Check

function isPalindromeString(str) {
  const cleanStr = str.toLowerCase().replace(/[^a-z0-9]/g, '');
  return cleanStr === cleanStr.split('').reverse().join('');
}

// Example usage
console.log(isPalindromeString("A man, a plan, a canal: Panama")); // true
console.log(isPalindromeString("hello")); // false

Binary Search Implementation

function binarySearch(arr, target) {
  let left = 0;
  let right = arr.length - 1;

  while (left <= right) {
    const mid = Math.floor((left + right) / 2);

    if (arr[mid] === target) return mid;

    if (arr[mid] < target) {
      left = mid + 1;
    } else {
      right = mid - 1;
    }
  }

  return -1; // Target not found
}

// Example usage
console.log(binarySearch([1, 2, 3, 4, 5, 6, 7, 8, 9, 10], 7)); // 6
console.log(binarySearch([1, 2, 3, 4, 5, 6, 7, 8, 9, 10], 11)); // -1

Armstrong Number Check

function isArmstrongNumber(num) {
  const digits = num.toString().split('');
  const power = digits.length;

  const sum = digits.reduce((acc, digit) => {
    return acc + Math.pow(parseInt(digit), power);
  }, 0);

  return sum === num;
}

// Example usage
console.log(isArmstrongNumber(153)); // true (1^3 + 5^3 + 3^3 = 153)
console.log(isArmstrongNumber(370)); // true (3^3 + 7^3 + 0^3 = 370)
console.log(isArmstrongNumber(123)); // false

Reverse a String

function reverseString(str) {
  return str.split('').reverse().join('');
}

// Example usage
console.log(reverseString("hello")); // "olleh"

TCS Digital Questions

Two Sum Problem

function twoSum(nums, target) {
  const numToIndex = {};

  for (let i = 0; i < nums.length; i++) {
    const complement = target - nums[i];

    if (complement in numToIndex) {
      return [numToIndex[complement], i];
    }

    numToIndex[nums[i]] = i;
  }

  return [-1, -1]; // No solution found
}

// Example usage
console.log(twoSum([2, 7, 11, 15], 9)); // [0, 1]

Find Duplicate in an Array

function findDuplicate(nums) {
  // Floyd's Tortoise and Hare (Cycle Detection)
  let slow = nums[0];
  let fast = nums[0];

  do {
    slow = nums[slow];
    fast = nums[nums[fast]];
  } while (slow !== fast);

  slow = nums[0];

  while (slow !== fast) {
    slow = nums[slow];
    fast = nums[fast];
  }

  return fast;
}

// Example usage
console.log(findDuplicate([1, 3, 4, 2, 2])); // 2

Longest Substring Without Repeating Characters

function lengthOfLongestSubstring(s) {
  const charMap = new Map();
  let maxLength = 0;
  let start = 0;

  for (let end = 0; end < s.length; end++) {
    const currentChar = s[end];

    if (charMap.has(currentChar)) {
      start = Math.max(charMap.get(currentChar) + 1, start);
    }

    charMap.set(currentChar, end);
    maxLength = Math.max(maxLength, end - start + 1);
  }

  return maxLength;
}

// Example usage
console.log(lengthOfLongestSubstring("abcabcbb")); // 3
console.log(lengthOfLongestSubstring("bbbbb")); // 1
console.log(lengthOfLongestSubstring("pwwkew")); // 3

Implement Merge Sort

function mergeSort(arr) {
  if (arr.length <= 1) return arr;

  const mid = Math.floor(arr.length / 2);
  const left = mergeSort(arr.slice(0, mid));
  const right = mergeSort(arr.slice(mid));

  return merge(left, right);
}

function merge(left, right) {
  const result = [];
  let leftIndex = 0;
  let rightIndex = 0;

  while (leftIndex < left.length && rightIndex < right.length) {
    if (left[leftIndex] < right[rightIndex]) {
      result.push(left[leftIndex]);
      leftIndex++;
    } else {
      result.push(right[rightIndex]);
      rightIndex++;
    }
  }

  return [...result, ...left.slice(leftIndex), ...right.slice(rightIndex)];
}

// Example usage
console.log(mergeSort([5, 3, 8, 4, 2, 1, 6])); // [1, 2, 3, 4, 5, 6, 8]

Kth Largest Element in an Array

function findKthLargest(nums, k) {
  // Quick select algorithm
  return quickSelect(nums, 0, nums.length - 1, nums.length - k);
}

function quickSelect(nums, left, right, kSmallest) {
  if (left === right) return nums[left];

  const pivotIndex = partition(nums, left, right);

  if (pivotIndex === kSmallest) {
    return nums[pivotIndex];
  } else if (pivotIndex < kSmallest) {
    return quickSelect(nums, pivotIndex + 1, right, kSmallest);
  } else {
    return quickSelect(nums, left, pivotIndex - 1, kSmallest);
  }
}

function partition(nums, left, right) {
  const pivot = nums[right];
  let i = left;

  for (let j = left; j < right; j++) {
    if (nums[j] <= pivot) {
      [nums[i], nums[j]] = [nums[j], nums[i]];
      i++;
    }
  }

  [nums[i], nums[right]] = [nums[right], nums[i]];
  return i;
}

// Example usage
console.log(findKthLargest([3, 2, 1, 5, 6, 4], 2)); // 5

Palindrome Number

function isPalindromeNumber(x) {
  if (x < 0) return false;

  const str = x.toString();
  const reverseStr = str.split('').reverse().join('');

  return str === reverseStr;
}

// Example usage
console.log(isPalindromeNumber(121)); // true
console.log(isPalindromeNumber(-121)); // false
console.log(isPalindromeNumber(10)); // false

Move Zeros in an Array

function moveZeroes(nums) {
  let nonZeroIndex = 0;

  // Move all non-zero elements to the front
  for (let i = 0; i < nums.length; i++) {
    if (nums[i] !== 0) {
      nums[nonZeroIndex] = nums[i];
      nonZeroIndex++;
    }
  }

  // Fill the rest with zeros
  for (let i = nonZeroIndex; i < nums.length; i++) {
    nums[i] = 0;
  }

  return nums;
}

// Example usage
console.log(moveZeroes([0, 1, 0, 3, 12])); // [1, 3, 12, 0, 0]

Maximum Subarray Problem (Kadane's Algorithm)

function maxSubArray(nums) {
  let maxSum = nums[0];
  let currentSum = nums[0];

  for (let i = 1; i < nums.length; i++) {
    currentSum = Math.max(nums[i], currentSum + nums[i]);
    maxSum = Math.max(maxSum, currentSum);
  }

  return maxSum;
}

// Example usage
console.log(maxSubArray([-2, 1, -3, 4, -1, 2, 1, -5, 4])); // 6

Valid Parentheses

function isValidParentheses(s) {
  const stack = [];
  const brackets = {
    '(': ')',
    '[': ']',
    '{': '}'
  };

  for (let char of s) {
    if (char in brackets) {
      stack.push(char);
    } else {
      const lastBracket = stack.pop();
      if (brackets[lastBracket] !== char) {
        return false;
      }
    }
  }

  return stack.length === 0;
}

// Example usage
console.log(isValidParentheses("()")); // true
console.log(isValidParentheses("()[]{}")); // true
console.log(isValidParentheses("(]")); // false

Climbing Stairs Problem

function climbStairs(n) {
  if (n <= 2) return n;

  let oneStepBefore = 2;
  let twoStepsBefore = 1;
  let ways = 0;

  for (let i = 3; i <= n; i++) {
    ways = oneStepBefore + twoStepsBefore;
    twoStepsBefore = oneStepBefore;
    oneStepBefore = ways;
  }

  return ways;
}

// Example usage
console.log(climbStairs(3)); // 3
console.log(climbStairs(5)); // 8

TCS Ninja Questions

Check if Array is Sorted

function isSorted(arr) {
  for (let i = 1; i < arr.length; i++) {
    if (arr[i] < arr[i-1]) {
      return false;
    }
  }
  return true;
}

// Example usage
console.log(isSorted([1, 2, 3, 4, 5])); // true
console.log(isSorted([1, 2, 4, 3, 5])); // false

Bubble Sort Algorithm

function bubbleSort(arr) {
  const n = arr.length;

  for (let i = 0; i < n; i++) {
    let swapped = false;

    for (let j = 0; j < n - i - 1; j++) {
      if (arr[j] > arr[j + 1]) {
        [arr[j], arr[j + 1]] = [arr[j + 1], arr[j]];
        swapped = true;
      }
    }

    // If no swapping occurred in this pass, array is sorted
    if (!swapped) break;
  }

  return arr;
}

// Example usage
console.log(bubbleSort([5, 3, 8, 4, 2])); // [2, 3, 4, 5, 8]

Sum of Array Elements

function sumArray(arr) {
  return arr.reduce((sum, num) => sum + num, 0);
}

// Example usage
console.log(sumArray([1, 2, 3, 4, 5])); // 15

Check for Prime Numbers in a Range

function primesInRange(start, end) {
  const primes = [];

  for (let num = start; num <= end; num++) {
    if (isPrime(num)) {
      primes.push(num);
    }
  }

  return primes;

  function isPrime(num) {
    if (num <= 1) return false;
    if (num <= 3) return true;

    if (num % 2 === 0 || num % 3 === 0) return false;

    let i = 5;
    while (i * i <= num) {
      if (num % i === 0 || num % (i + 2) === 0) return false;
      i += 6;
    }

    return true;
  }
}

// Example usage
console.log(primesInRange(10, 30)); // [11, 13, 17, 19, 23, 29]

Count the Frequency of Characters in a String

function characterFrequency(str) {
  const frequency = {};

  for (let char of str) {
    frequency[char] = (frequency[char] || 0) + 1;
  }

  return frequency;
}

// Example usage
console.log(characterFrequency("hello")); // { h: 1, e: 1, l: 2, o: 1 }

Find the Second Largest Element in an Array

function findSecondLargest(arr) {
  if (arr.length < 2) return -1;

  let largest = arr[0];
  let secondLargest = -Infinity;

  for (let i = 1; i < arr.length; i++) {
    if (arr[i] > largest) {
      secondLargest = largest;
      largest = arr[i];
    } else if (arr[i] < largest && arr[i] > secondLargest) {
      secondLargest = arr[i];
    }
  }

  return secondLargest === -Infinity ? -1 : secondLargest;
}

// Example usage
console.log(findSecondLargest([12, 35, 1, 10, 34, 1])); // 34

Perfect Number Check

function isPerfectNumber(num) {
  if (num <= 1) return false;

  let sum = 1; // Start with 1 as every number is divisible by 1

  for (let i = 2; i <= Math.sqrt(num); i++) {
    if (num % i === 0) {
      sum += i;
      if (i !== num / i) {
        sum += num / i;
      }
    }
  }

  return sum === num;
}

// Example usage
console.log(isPerfectNumber(6)); // true (6 = 1 + 2 + 3)
console.log(isPerfectNumber(28)); // true (28 = 1 + 2 + 4 + 7 + 14)
console.log(isPerfectNumber(12)); // false

Factorial of a Number

function factorial(n) {
  if (n < 0) return null;
  if (n <= 1) return 1;

  let result = 1;
  for (let i = 2; i <= n; i++) {
    result *= i;
  }

  return result;
}

// Example usage
console.log(factorial(5)); // 120

Sort an Array of 0s, 1s, and 2s (Dutch National Flag Problem)

function sortColors(nums) {
  let low = 0;
  let mid = 0;
  let high = nums.length - 1;

  while (mid <= high) {
    if (nums[mid] === 0) {
      [nums[low], nums[mid]] = [nums[mid], nums[low]];
      low++;
      mid++;
    } else if (nums[mid] === 1) {
      mid++;
    } else if (nums[mid] === 2) {
      [nums[mid], nums[high]] = [nums[high], nums[mid]];
      high--;
    }
  }

  return nums;
}

// Example usage
console.log(sortColors([2, 0, 2, 1, 1, 0])); // [0, 0, 1, 1, 2, 2]

DSA Questions by Role

NQT DSA Questions

1. Reverse a Linked List
2. Fibonacci Series Using Recursion
3. Check if a String is Palindrome
4. Find the Middle of a Linked List
5. Bubble Sort Algorithm
6. Remove Duplicates from a Sorted Linked List
7. Maximum Sum Subarray (Kadane's Algorithm)
8. Check if a Tree is a Binary Search Tree
9. Binary Search
10. Insertion Sort Algorithm
11. Find the nth Node from the End of a Linked List
12. Detect Loop in a Linked List
13. Merge Two Sorted Arrays
14. Balanced Parentheses
15. Intersection of Two Linked Lists
16. Sorting a Stack Using Recursion
17. Find the Minimum Element in a Stack
18. Reverse a String Using Stack
19. Check for Anagrams
20. Move Zeroes to the End of Array

Digital DSA Questions

1. Two Sum Problem
2. Find the Longest Palindromic Substring
3. Merge Intervals
4. Quick Sort Algorithm
5. Find the Kth Largest Element in an Array
6. Trapping Rain Water
7. Longest Common Subsequence
8. Top K Frequent Elements
9. Binary Tree Level Order Traversal
10. Longest Increasing Subsequence
11. Rotate Matrix by 90 Degrees
12. Nth Fibonacci Number Using Dynamic Programming
13. Flatten a Multilevel Doubly Linked List
14. Find the First Missing Positive
15. Zigzag Level Order Traversal of a Binary Tree
16. Find the Lowest Common Ancestor in a Binary Tree
17. Detect Cycle in a Directed Graph
18. Median of Two Sorted Arrays
19. Merge K Sorted Linked Lists
20. Coin Change Problem

Ninja DSA Questions

1. Check if Array is Sorted
2. Find the Missing Number in an Array
3. Find the Second Largest Element in an Array
4. Find Intersection of Two Arrays
5. Detect Cycle in an Undirected Graph
6. Remove Duplicates from Unsorted Linked List
7. Count Inversions in an Array
8. Reverse a Queue Using Recursion
9. Convert Binary Tree to Doubly Linked List
10. Check for Balanced Binary Tree
11. Find Majority Element in an Array
12. Sort Colors
13. Remove Loop in Linked List
14. Check if a Binary Tree is Symmetric
15. Find Duplicates in O(n) Time and O(1) Space
16. Find the Median of a Stream of Integers
17. K Closest Points to Origin
18. Word Search
19. Serialize and Deserialize a Binary Tree
20. Next Greater Element