The string “PAYPALISHIRING” is written in a zigzag pattern on a given number of rows like this: (you may want to display this pattern in a fixed font ...

Write a function to find the longest common prefix string amongst an array of strings. If there is no common prefix, return an empty string “”. Exampl ...

Given a string s consists of upper/lower-case alphabets and empty space characters ‘ ‘, return the length of last word in the string. If the last word ...

Given two binary strings, return their sum (also a binary string). The input strings are both non-empty and contains only characters 1 or 0. ExampleNo ...

Given two binary trees, write a function to check if they are the same or not. Two binary trees are considered the same if they are structurally ident ...

Given a binary tree, check whether it is a mirror of itself (ie, symmetric around its center). For example, this binary tree [1,2,2,3,4,4,3] is symmet ...

A binary tree is univalued if every node in the tree has the same value. Return true if and only if the given tree is univalued. ExampleNo.1 Input: [1 ...

We have an array A of integers, and an array queries of queries. For the i-th query val = queries[i][0], index = queries[i][1], we add val to A[index] ...

Given an array of 2n integers, your task is to group these integers into n pairs of integer, say (a1, b1), (a2, b2), …, (an, bn) which makes sum of mi ...

Write a class RecentCounter to count recent requests. It has only one method: ping(int t), where t represents some time in milliseconds. Return the nu ...