DescriptionGiven a roman numeral, convert it to an integer. Input is guaranteed to be within the range from 1 to 3999. The original problem is here. The original code is here.

DescriptionGiven a string S, find the longest palindromic substring in S. You may assume that the maximum length of S is 1000, and there exists one unique longest palindromic substring. The original p

DescriptionImplement atoi to convert a string to an integer. The original problem is here. The original code is here.

DescriptionGiven an array S of n integers, are there elements a, b, c, and d in S such that a + b + c + d = target? Find all unique quadruplets in the array which gives the sum of target. Note:Element

DescriptionGiven an array S of n integers, find three integers in S such that the sum is closest to a given number, target. Return the sum of the three integers. You may assume that each input would h

DescriptionGiven an array S of n integers, are there elements a, b, c in S such that a + b + c = 0? Find all unique triplets in the array which gives the sum of zero. Note:Elements in a triplet (a,b,c

DescriptionGiven a binary tree and a sum, find all root-to-leaf paths where each path’s sum equals the given sum. For example:Given the below binary tree and sum = 22, 5 / \

DescriptionEvaluate the value of an arithmetic expression in Reverse Polish Notation. Valid operators are +, -, *, /. Each operand may be an integer or another expression. Some examples: ["2"

DescriptionImplement next permutation, which rearranges numbers into the lexicographically next greater permutation of numbers. If such arrangement is not possible, it must rearrange it as the lowest

DescriptionGiven a linked list, reverse the nodes of a linked list k at a time and return its modified list. If the number of nodes is not a multiple of k then left-out nodes in the end should remain