A robot is located at the top-left corner of a m x n grid (marked ‘Start’ in the diagram below). The robot can only move either down or right at any p ...

A robot is located at the top-left corner of a m x n grid. The robot can only move either down or right at any point in time. The robot is trying to r ...

You are climbing a stair case. It takes n steps to reach to the top. Each time you can either climb 1 or 2 steps. In how many distinct ways can you cl ...

Evaluate the value of an arithmetic expression in Reverse Polish Notation. Valid operators are +, -, *, /. Each operand may be an integer or another e ...

Given a string containing just the characters ‘(‘, ‘)’, ‘{‘, ‘}’, ‘[‘ and ‘]’, determine if the input string is valid. An input string is valid if: Op ...

Design a stack that supports push, pop, top, and retrieving the minimum element in constant time. push(x) – Push element x onto stack. pop() – Remove ...

Given a reference of a node in a connected undirected graph, return a deep copy (clone) of the graph. Each node in the graph contains a val (int) and ...

Given a roman numeral, convert it to an integer. Input is guaranteed to be within the range from 1 to 3999. Roman numerals are represented by seven di ...

Given an integer, convert it to a roman numeral. Input is guaranteed to be within the range from 1 to 3999. Roman numerals are represented by seven di ...

Given a matrix of m x n elements (m rows, n columns), return all elements of the matrix in spiral order. ExampleNo.1Input:[ [ 1, 2, 3 ], [ 4, 5, 6 ], ...