Leetcode Permutations
In this leetcode problem premutation we have given an array of distinct integers, print all of its possible permutations. Examples Input arr[] = {1, 2, 3} Output 1 2 3 1 3 2 2 1 3 2 3 1 3 1 2 3 2 1 Input arr[] = {1, 2, …
Kth Smallest Element in a BST
In this problem, we have given a BST and a number k, find the kth smallest element in a BST. Examples Input tree[] = {5, 3, 6, 2, 4, null, null, 1} k = 3 Output 3 Input tree[] = {3, 1, 4, null, 2} k = 1 Output 1 …
Search an Element in Sorted Rotated Array
In search in sorted rotated array problem we have given a sorted and rotated array and an element, check if the given element is present in the array or not. Examples Input nums[] = {2, 5, 6, 0, 0, 1, 2} target = 0 Output true Input nums[] = {2, …
Valid Parenthesis String
In the valid parenthesis string problem we have given a string containing ‘(‘, ‘)‘ and ‘*‘, check if the string is balanced if ‘*‘ can be replaced with ‘(‘, ‘)‘ or an empty string. Examples Input “()” Output true Input “*)” Output true Input “(*))” Output true Naive Approach for …
Interval Tree
In the interval tree problem, we have given a set of intervals and three types of queries addInterval(x,y): Add an interval (x,y) to the set removeInterval(x,y): Remove an interval (x,y) from the set checkInterval(x,y): Check if interval (x,y) overlaps with some existing interval Design a data structure( Interval Tree ) …
Set Matrix Zeroes
In the set matrix zeroes problem, we have given a (n X m) matrix, if an element is 0, set its entire row and column 0. Examples Input: { [1, 1, 1] [1, 0, 1] [1, 1, 1] } Output: { [1, 0, 1] [0, 0, 0] [1, 0, 1] …
Lowest Common Ancestor
Given the root of a binary tree and two nodes n1 and n2, find the LCA(Lowest Common Ancestor) of the nodes. Example What is Lowest Common Ancestor(LCA)? The ancestors of a node n are the nodes present in the path between root and node. Consider the binary tree shown in …
Queue using Stacks
In queue using a stack problem, we have to implement the following functions of a queue using the standard functions of stack data structure, Enqueue: Add an element to the end of the queue Dequeue: Remove an element from the start of the queue Example Input: Enqueue(5) Enqueue(11) Enqueue(39) Dequeue() …