150. Evaluate Reverse Polish Notation

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

224. Basic Calculator

Implement a basic calculator to evaluate a simple expression string. The expression string may contain open ( and closing parentheses ), the plus + or minus s...

134. Gas Station

Question: There are N gas stations along a circular route, where the amount of gas at station i is gas[i]. You have a car with an unlimited gas tank and it costs

42. Trapping Rain Water

Given n non-negative integers representing an elevation map where the width of each bar is 1, compute how much water it is able to trap after raining. For example, Given [0,1,0,2,1,0,1,3,2,...