400+ Leela Electric Interview Questions and Answers

Q2. Generate Binary Strings with No Consecutive 1s

Given an integer K, your task is to produce all binary strings of length 'K' that do not contain consecutive '1's.

Input:

The input begins with an integer 'T', the...read more

Q3. Reverse Linked List Problem Statement

Given a singly linked list of integers, return the head of the reversed linked list.

Example:

Initial linked list: 1 -> 2 -> 3 -> 4 -> NULL
Reversed linked list: 4 -> 3 -> 2...read more

Q4. Longest Consecutive Sequence Problem Statement

You are provided with an unsorted array/list ARR of N integers. Your task is to determine the length of the longest consecutive sequence present in the array.

Expl...read more

Q5. SpecialStack Design Problem

Design a stack that efficiently supports the getMin() operation in O(1) time with O(1) extra space. This stack should include the following operations: push(), pop(), top(), isEmpty(...read more

Q6. Minimum Number of Coins Problem

Dora, on her visit to India, decides to enjoy Indian cuisine where payments are accepted only in specific denominations. Your task is to help Dora obtain the minimum number of co...read more

Q7. Subsequence Determination Problem

Your task is to verify if the given string STR1 is a subsequence of the string STR2. A subsequence means characters from STR2 are retained in their original order but some (or ...read more

Q8. Ways To Make Coin Change

Given an infinite supply of coins of varying denominations, determine the total number of ways to make change for a specified value using these coins. If it's not possible to make the c...read more

Q9. Kth Smallest Element Problem Statement

You are provided with an array of integers ARR of size N and an integer K. Your task is to find and return the K-th smallest value present in the array. All elements in th...read more

Q10. Search In Rotated Sorted Array Problem Statement

Given a sorted array of distinct integers that has been rotated clockwise by an unknown amount, you need to search for a specified integer in the array. For each...read more

Q11. Sum of Squares of First N Natural Numbers Problem Statement

You are tasked with finding the sum of squares of the first N natural numbers for given test cases.

Input:

The first line contains an integer 'T', the...read more

Q12. Permutations Problem Statement

Given an array of distinct integers, find all possible permutations of the array.

Explanation:

A permutation is a mathematical way of determining the number of possible arrangemen...read more

Q13. String Transformation Problem

Given a string (STR) of length N, you are tasked to create a new string through the following method:

Select the smallest character from the first K characters of STR, remove it fr...read more

Q14. Geometric Progression Subsequences Problem Statement

Given an array of ‘N’ integers, determine the number of subsequences of length 3 that form a geometric progression with a specified common ratio ‘R’.

Explana...read more

Q15. Middle of a Linked List

You are given the head node of a singly linked list. Your task is to return a pointer pointing to the middle of the linked list.

If there is an odd number of elements, return the middle ...read more

Q16. Minimum Subset Sum Difference Problem

Given an array of non-negative integers, your task is to partition this array into two subsets such that the absolute difference between the sums of the subsets is minimize...read more

Q17. Reverse Alternate K Nodes Problem Statement

You are given a singly linked list of integers along with a positive integer 'K'. The task is to modify the linked list by reversing every alternate 'K' nodes of the ...read more

Q18. Detect and Remove Loop in Linked List

For a given singly linked list, identify if a loop exists and remove it, adjusting the linked list in place. Return the modified linked list.

Expected Complexity:

Aim for a...read more

Q19. Sort an Array in Wave Form

You are given an unsorted array ARR. Your task is to sort it so that it forms a wave-like array.

Input:

The first line contains an integer 'T', the number of test cases.
For each test ...read more

Q20. Find Nodes at a Specific Distance from Target in a Binary Tree

Given a binary tree, a target node within this tree, and an integer K, identify and return all nodes that are exactly K edges away from the target ...read more

Q21. Rotting Oranges Problem Statement

You are given a grid containing oranges where each cell of the grid can contain one of the three integer values:

• 0 - representing an empty cell
• 1 - representing a fresh orange...read more

Q22. Min Stack Problem Statement

Design a special stack that supports the following operations in constant time:

1. Push(num): Insert the given number into the stack.
2. Pop: Remove and return the top element from the st...read more

Q23. Minimum Falling Path Sum Problem Statement

Given a square array VEC of integers with N rows and N columns, you need to determine the minimum sum of a falling path through this square array. The array has equal ...read more

Q24. Group Anagrams Problem Statement

Given an array or list of strings called inputStr, your task is to return the strings grouped as anagrams. Each group should contain strings that are anagrams of one another.

An...read more

Q25. Delete a Node from Linked List Problem Statement

Given a linked list of integers, your task is to implement a function that deletes a node at a specified position, 'POS'.

If the specified position is greater th...read more

Q26. Segregate Even and Odd Nodes in a Linked List

You are given the head node of a singly linked list head. Your task is to modify the linked list so that all the even-valued nodes appear before all the odd-valued ...read more

Q27. Distinct Subsets Count

Given an array arr of N integers that may include duplicates, determine the number of subsets of this array containing only distinct elements.

The result should be returned modulo 10⁹ + 7...read more

Q28. Reverse a Linked List Problem Statement

You are given a Singly Linked List of integers. Your task is to reverse the Linked List by changing the links between nodes.

Input:

The first line of input contains a sin...read more

Q29. Ninja Technique Problem Statement

Implement a function that determines whether a given numeric string contains any substring whose integer value equals the product of two consecutive integers. The function shou...read more

Q30. Clone Linked List with Random Pointer

Your task is to create a deep copy of a linked list, where each node has two pointers: one that points to the next node in the list, and a 'random' pointer which can point ...read more

Q31. Quick Sort Problem Statement

Sort the given array of integers in ascending order using the quick sort algorithm. Quick sort is a divide-and-conquer algorithm where a pivot point is chosen to partition the array...read more

Q32. Distributing Coins in a Binary Tree

You are provided with the root of a binary tree that consists of 'N' nodes. Each node in this tree contains coins, and the total number of coins across all nodes is equal to ...read more

Q33. Replace 0s Problem Statement

You are given a matrix where every element is either a 1 or a 0. The task is to replace 0 with 1 if it is surrounded by 1s. A 0 (or a set of 0s) is considered to be surrounded by 1s...read more

Number In Arithmetic Progression Problem

Given three integers X, C, and Y, where X is the first term of an arithmetic sequence with a common difference of C, determine if Y is part of this arithmetic sequence.

Q35. Spiral Order Traversal of a Binary Tree Problem Statement

Given a binary tree with 'N' nodes, your task is to print the nodes in spiral order traversal.

Example:

Input:

The binary tree is represented in level o...read more

Q36. Minimum Insertions to Make a String Palindrome

Determine the minimal number of characters needed to insert into a given string STR to transform it into a palindrome.

Example:

Input:

STR = "abcaa"

Output:

2

Expl...read more

Q37. Zigzag Traversal of Binary Tree

Given a binary tree with integer values in its nodes, your task is to print the zigzag traversal of the tree.

Note:

In zigzag order, level 1 is printed from left to right, level ...read more

Q38. Decode String Problem Statement

Your task is to decode a given encoded string back to its original form.

Explanation:

An encoded string format is [encoded_string], where the 'encoded_string' inside the square b...read more

Q39. Problem: Sort an Array of 0s, 1s, and 2s

Given an array/list ARR consisting of integers where each element is either 0, 1, or 2, your task is to sort this array in increasing order.

Input:

The input starts with...read more

Q40. Sub Sort Problem Statement

You are given an integer array ARR. Determine the length of the shortest contiguous subarray which, when sorted in ascending order, results in the entire array being sorted in ascendi...read more

Q41. Longest Common Subsequence Problem Statement

Given two strings STR1 and STR2, determine the length of their longest common subsequence.

A subsequence is a sequence that can be derived from another sequence by d...read more

Q42. Minimum Fountains Activation Problem

In this problem, you have a one-dimensional garden of length 'N'. Each position from 0 to 'N' has a fountain that can provide water to the garden up to a certain range. Thus...read more

Q43. Maximum Subarray Sum Problem Statement

Given an array ARR consisting of N integers, your goal is to determine the maximum possible sum of a non-empty contiguous subarray within this array.

Example of Subarrays:...read more

Q44. Delete a Node in a Linked List

Given a reference to a node in a singly linked list, your task is to delete that node. Every node in the list has a unique value. The head of the linked list will not be provided....read more

Q45. Maze Obstacle Problem Statement

Given an N * M grid representing a maze with obstacles, compute and return the total number of distinct paths from the top-left cell to the bottom-right cell. A cell in the maze ...read more

Q46. Inorder Successor in a Binary Tree

Find the inorder successor of a given node in a binary tree. The inorder successor is the node that appears immediately after the given node during an inorder traversal. If th...read more

Q47. Group Anagrams Together

Given an array/list of strings STR_LIST, group the anagrams together and return each group as a list of strings. Each group must contain strings that are anagrams of each other.

Example:...read more

Q48. 0-1 Knapsack Problem Statement

A thief is robbing a store and can carry a maximal weight 'W' in his knapsack. There are 'N' items, where the i-th item has a weight 'wi' and value 'vi'. Consider the maximum weig...read more

Q49. Connect Ropes with Minimum Cost

Given 'N' ropes, each having different lengths, your task is to connect these ropes into one single rope. The cost to connect two particular ropes is equal to the sum of their le...read more

Q50. Parth's OCD Challenge

Parth, a budding programmer, has received an array 'ARR' of 'N' positive integers. His OCD is triggered whenever an odd number appears at an even index or an even number at an odd index in...read more

Q51. Delete Middle Node Problem Statement

You are given a singly linked list of integers. The task is to delete the middle node of this list.

Note:

1. If the list has no middle node, return an empty list (NULL). 2. ...read more

Q52. Adding Two Linked Lists

Given two singly linked lists, with each list representing a positive number without leading zeros, your task is to add these two numbers and return the result in the form of a new linke...read more

Q53. Merge Sort Task

Given a sequence of numbers, denoted as ARR, your task is to return a sorted sequence of ARR in non-descending order using the Merge Sort algorithm.

Example:

Explanation:

The Merge Sort algorith...read more

Q54. Cube Sum Pairs Problem Statement

Given a positive integer N, find the number of ways to express N as a sum of cubes of two integers, A and B, such that:

N = A^3 + B^3

Ensure you adhere to the following conditio...read more

Q55. Sort 0 1 2 Problem Statement

Given an integer array arr of size 'N' containing only 0s, 1s, and 2s, write an algorithm to sort the array.

Input:

The first line contains an integer 'T' representing the number of...read more

Q56. All Pairs with Target Sum

Given an array of integers ARR with length 'N' and an integer 'Target', the task is to find all unique pairs of elements that add up to the 'Target'.

Input:

First line: Integer 'T' - n...read more

Q57. BST Iterator Problem Statement

You are tasked with creating a class named BSTIterator that acts as an iterator for the inorder traversal of a binary search tree. Implement the following functions:

1. BSTIterator(...read more

Q58. Smallest Integer Not Representable as Subset Sum

Given a non-decreasing sorted array ARR of N positive numbers, determine the smallest positive integer that cannot be expressed as the sum of elements from any p...read more

Q59. Closest Leaf in a Binary Tree

Ninja is stuck in a maze represented as a binary tree, and he is at a specific node ‘X’. Help Ninja find the shortest path to the nearest leaf node, which is considered an exit poi...read more

Q60. Job Sequencing Problem Statement

You are provided with a N x 2 2-D array called Jobs consisting of N jobs. In this array, Jobs[i][0] represents the deadline of the i-th job, while Jobs[i][1] indicates the profi...read more

Q61. LCA in a Binary Search Tree

You are given a binary search tree (BST) containing N nodes. Additionally, you have references to two nodes, P and Q, within this BST.

Your task is to determine the Lowest Common Anc...read more

Q62. Minimum Characters to Make a String Palindrome

Given a string STR of length N, determine the minimum number of characters to be added to the front of the string to make it a palindrome.

Input:

The first line co...read more

Q64. Running Median Problem

Given a stream of integers, calculate and print the median after each new integer is added to the stream.

Output only the integer part of the median.

Example:

Input:

N = 5 
Stream = [2, 3,...read more

Q65. Minimum Number of Platforms Required

You are provided with two arrays, AT and DT, representing the arrival and departure times of all trains arriving at a railway station.

Your task is to determine the minimum ...read more

Diameter of a Binary Tree Problem Statement

Given a binary tree, return the length of its diameter. The diameter of a binary tree is defined as the length of the longest path between any two nodes in the tree.

Q67. Ceil Value from BST Problem Statement

Given a Binary Search Tree (BST) and an integer, write a function to return the ceil value of a particular key in the BST.

The ceil of an integer is defined as the smallest...read more

Q68. Bottom Right View of Binary Tree Problem Statement

Your task is to identify and return the bottom right view of a given binary tree.

This involves viewing the binary tree from an angle of 45 degrees from the bo...read more

Q69. Subtree of Another Tree Problem Statement

Given two binary trees, T and S, determine whether S is a subtree of T. The tree S should have the same structure and node values as a subtree of T.

Explanation:

A subt...read more

Q70. Count Ways to Reach the N-th Stair Problem Statement

You are provided with a number of stairs, and initially, you are located at the 0th stair. You need to reach the Nth stair, and you can climb one or two step...read more

Q71. Rotate Matrix by 90 Degrees Problem Statement

Given a square matrix 'MATRIX' of non-negative integers, rotate the matrix by 90 degrees in an anti-clockwise direction using only constant extra space.

Input:

The ...read more

Q72. Minimize Cash Flow Problem

You are provided with a list of 'transactions' involving 'n' friends who owe each other money. Each entry in the list contains information about a receiver, sender, and the transactio...read more

Q73. Container with Most Water Problem Statement

Given a sequence of 'N' space-separated non-negative integers A[1], A[2], ..., A[i], ..., A[n], where each number in the sequence represents the height of a line draw...read more

Q74. Floor Value of X Problem Statement

Given a sorted array A and an integer X, your task is to find and return the floor value of X in the array.

The floor value of X is the largest element in array A which is sma...read more

Q75. Buy and Sell Stock Problem Statement

Imagine you are Harshad Mehta's friend, and you have been given the stock prices of a particular company for the next 'N' days. You can perform up to two buy-and-sell transa...read more

Q76. Integer to Roman Conversion

Given an integer N, convert it to its corresponding Roman numeral representation. Roman numerals comprise seven symbols: I, V, X, L, C, D, and M.

Example:

Input:

N = 2

Output:

II

Exp...read more

Q77. Factorial Calculation Problem Statement

Develop a program to compute the factorial of a given integer 'n'.

The factorial of a non-negative integer 'n', denoted as n!, is the product of all positive integers les...read more

Q78. Next Greater Element Problem Statement

Given a list of integers of size N, your task is to determine the Next Greater Element (NGE) for every element. The Next Greater Element for an element X is the first elem...read more

Q79. Cousin Nodes in a Binary Tree

Determine if two nodes in a binary tree are cousins. Nodes are considered cousins if they are at the same level and have different parents.

Explanation:

In a binary tree, each node...read more

Q80. Trapping Rain Water Problem Statement

You are given a long type array/list ARR of size N, representing an elevation map. The value ARR[i] denotes the elevation of the ith bar. Your task is to determine the tota...read more

Q81. Kth Smallest and Largest Element Problem Statement

You are provided with an array 'Arr' containing 'N' distinct integers and a positive integer 'K'. Your task is to find the Kth smallest and Kth largest element...read more

Q82. Problem Statement: Parity Move

You have an array of integers, and your task is to modify the array by moving all even numbers to the beginning while placing all odd numbers at the end. The order within even and...read more

Q83. Anagram Pairs Verification Problem

Your task is to determine if two given strings are anagrams of each other. Two strings are considered anagrams if you can rearrange the letters of one string to form the other...read more

Q84. Circular Move Problem Statement

You have a robot currently positioned at the origin (0, 0) on a two-dimensional grid, facing the north direction. You are given a sequence of moves in the form of a string of len...read more

Q85. Binary Tree Diameter Problem Statement

Given a binary tree, determine the length of its diameter. The diameter is defined as the longest path between any two end nodes in the tree. The path's length is represen...read more

Q86. Colorful Knapsack Problem

You are given a set of 'N' stones, each with a specific weight and color. The goal is to fill a knapsack with exactly 'M' stones, choosing one stone of each color, so that the total we...read more

Q87. Odd Even Levels in Binary Tree

Given a binary tree, the task is to compute the modulus of the difference between the sum of nodes at odd levels and the sum of nodes at even levels.

Input:

The first line contain...read more

Q88. Lexicographically Smallest Array Problem Statement

You are given an array ARR of 'N' integers and a positive integer 'K'.

Your task is to determine the lexicographically smallest array that can be obtained by p...read more

Q89. Prerequisite Task Completion Verification

Given a positive integer 'N', representing the number of tasks, and a list of dependency pairs, determine if it is possible to complete all tasks considering these prer...read more

Q91. Search in a Row-wise and Column-wise Sorted Matrix Problem Statement

You are given an N * N matrix of integers where each row and each column is sorted in increasing order. Your task is to find the position of ...read more

Q92. Find the Longest Palindromic Substring

Given a string ‘S’ composed of lowercase English letters, your task is to identify the longest palindromic substring within ‘S’.

If there are multiple longest palindromic ...read more

Q93. Print Nodes at Distance K from a Given Node

Given an arbitrary binary tree, a node of the tree, and an integer 'K', find all nodes that are at a distance K from the specified node, and return a list of these no...read more

Q95. Find Subarray with Given Sum

Given an array ARR of N integers and an integer S, determine if there exists a subarray (of positive length) within the given array such that the sum of its elements equals S. If su...read more

Q96. Diagonal Traversal of a Binary Tree

Given a binary tree of integers, find its diagonal traversal. Refer to the example for clarification on diagonal traversal.

Example:

Explanation:

Consider lines at an angle o...read more

Q98. Rahul And Minimum Subarray Challenge

Rahul is learning about arrays and lists. His teacher gave him a task to find the length of the smallest subarray in a given array 'ARR' of size 'N' with its sum greater tha...read more

Q99. LRU Cache Design Question

Design a data structure for a Least Recently Used (LRU) cache that supports the following operations:

1. get(key) - Return the value of the key if it exists in the cache; otherwise, re...read more