Evaluate a given expression
Given an expression containing numeric operands with addition and subtraction operators, evaluate it. The expression may contain sub-expressions enclosed in opening and closing braces.
Category: Stack
Construct a string from an encoded sequence
A string that may contain multiple consecutive instances of the same value is encoded to only store that value and its count. Given such an encoded sequence, decode it.
Find the previous smaller element for each array element
Given an integer array, find the previous smaller element for every array element. The previous smaller element of a number x is the first smaller number to the left of x in the array.
Check whether the leaf traversal of given binary trees is the same or not
Given two binary trees, check whether the leaf traversals of both trees are the same or not.
Construction of an expression tree
Construct an expression tree from a given postfix notation and print the infix notation. The binary expression tree is a binary tree whose leaves are operands, such as constants or variable names, and the other nodes contain operators.
Print complete Binary Search Tree (BST) in increasing order
Given a level order representation of a complete binary search tree, print its elements in increasing order.
Find the next greater element for every element in a circular array
Given a circular integer array, find the next greater element for every element in it. The next greater element of an element x in the array is the first larger number to the next of x.
Find the next greater element for every array element
Given an integer array, find the next greater element for every array element. The next greater element of a number x is the first greater number to the right of x in the array.
Invert alternate levels of a perfect binary tree
Write an efficient algorithm to invert alternate levels of a perfect binary tree.
Find all elements in an array that are greater than all elements to their right
Given an unsorted integer array, print all greater elements than all elements present to their right.
Implement a stack using the queue data structure
This post will implement a stack using the queue data structure. In other words, design a stack that supports push and pop operations using standard enqueue and dequeue operations of the queue.
Depth-First Search (DFS) vs Breadth-First Search (BFS)
This post will cover the difference between the Depth–first search (DFS) and Breadth–first search (BFS) algorithm used to traverse/search tree or graph data structure.