Coding Ninjas Logo

Home > Data Structures and Algorithms Questions

Data Structures and Algorithms Questions

Below is a compiled list of Data Structures and Algorithms interview questions that will help you conquer that upcoming interview of yours!

  1. What is asymptotic analysis of an algorithm?

  2. Write a program to find the node at which the intersection of two singly linked lists begins.

    Input: intersectVal = 8, listA = [4,1,8,4,5], listB = [5,0,1,8,4,5], skipA = 2, skipB = 3 Output: Reference of the node with value = 8 Input Explanation: The intersected node's value is 8 (note that this must not be 0 if the two lists intersect). From the head of A, it reads as [4,1,8,4,5]. From the head of B, it reads as [5,0,1,8,4,5]. There are 2 nodes before the intersected node in A; There are 3 nodes before the intersected node in B.

  3. How to find Loop in Linked List?

  4. What is hashing technique? Describe in brief.

  5. Given an Array of Integers find the maximum product of increasing subsequence of size 3. If a valid subsequence cannot be formed, print -1.

  6. Convert Binary Number in a Linked List to Integer.

  7. Minimum Depth of a Binary Tree

  8. Longest String Chain

    Given a list of words, each word consists of English lowercase letters.
    Let's say word1 is a predecessor of word2 if and only if we can add exactly one letter anywhere in word1 to make it equal to word2.
    For example, "abc" is a predecessor of "abac".
    A word chain is a sequence of words [word_1, word_2, ..., word_k] with k >= 1, where word_1 is a predecessor of word_2, word_2 is a predecessor of word_3, and so on.
    Return the longest possible length of a word chain with words chosen from the given list of words.

    Example 1:

    Input: ["a","b","ba","bca","bda","bdca"]
    Output: 4
    Explanation: one of the longest word chain is "a","ba","bda","bdca".

    Note:

    1. 1 <= words.length <= 1000
    2. 1 <= words[i].length <= 16
    3. words[i] only consists of English lowercase letters.

  9. How do you find the largest and smallest number in an unsorted integer array?

  10. Given two binary trees, check if they are the same or not.

  11. Write a program to know the house number of houses that are paying more rent than the neighbours.

  12. I have a MXN array and want to return all possible combinations of M size. Let me give you an example, there's a 3X3 array. The result should be 27 combinations.

  13. Puppy Treat (Array)

  14. Given a BST, convert it into a sorted linked list. Return the head of LL.

  15. Search an element in a rotated sorted array . Do it in O(logn).

  16. Given a list A of N distinct integer numbers, you can sort the list by moving an element to the end of the list. Find the minimum number of moves required to sort the list using this method in ascending order.

  17. Define Externalizable Interface and itspurpose with examples.

  18. Given a number n, find the smallest number that has same set of digits as n and is greater than n. If n is the greatest possible number with its set of digits, then print “not possible”.

  19. Best Time To Buy And Sell II

    Say you have an array prices for which the ith element is the price of a given stock on day i.
    Design an algorithm to find the maximum profit. You may complete as many transactions as you like (i.e., buy one and sell one share of the stock multiple times).
    Note: You may not engage in multiple transactions at the same time (i.e., you must sell the stock before you buy again).

    Example:

    Input:[7,1,5,3,6,4]
    Output: 7
    Explanation:Buy on day 2 (price = 1) and sell on day 3 (price = 5), profit = 5-1 = 4.
    Then buy on day 4 (price = 3) and sell on day 5 (price = 6), profit = 6-3 = 3.

  20. Rotting oranges question.🍊

  21. What is LRU Cache? Design and implements the LRU cache.

  22. Given n, how many structurally unique BST's (binary search trees) that store values 1 ... n?

  23. Given a bitonic sequence of n distinct elements, write a program to find a given element x in the bitonic sequence in O(log n) time. A Bitonic Sequence is a sequence of numbers which is first strictly increasing then after a point strictly decreasing.

    Example:
    Input : arr[] = {-3, 9, 8, 20, 17, 5, 1}
    key = 20
    Output : Found at index 3

  24. Find the count of distinct element in the given array in O(n) time.

  25. Given a singly linked list, determine if it is a palindrome, in O(1) time and O(1) space.
    Constraint: Explicit space not allowed (Hint :Use Recursion Stack).

  26. Why QuickSort is preferred for arrays and MergeSort for linked lists?

  27. What is LCA in binary tree explain and how to find it in binary search tree?