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You are playing the following Flip Game with your friend: Given a string that contains only these two characters:  +  and  - , you and your...

1. Min Stack Design a stack that supports push, pop, top, and retrieving the minimum element in constant time. push(x) -- Push element x...

A strobogrammatic number is a number that looks the same when rotated 180 degrees (looked at upside down). Find all strobogrammatic numbe...

Given an array of meeting time intervals consisting of start and end times  [[s1,e1],[s2,e2],...]  (s i  < e i ), find the minimum numbe...

According to the  Wikipedia's article : "The  Game of Life , also known simply as  Life , is a cellular automaton devised by the B...

Given two integers representing the numerator and denominator of a fraction, return the fraction in string format. If the fractional part...

Implement an iterator to flatten a 2d vector. For example, Given 2d vector = [ [1,2], [3], [4,5,6] ] By calling  next  repeat...