摘要：
Evaluate the value of an arithmetic expression in Reverse Polish Notation. Valid operators are+,-,*,/. Each operand may be an integer or another expre 阅读全文
摘要：
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. 阅读全文
摘要：
Given a string containing just the characters'('and')', find the length of the longest valid (well-formed) parentheses substring. For"(()", the longes 阅读全文
摘要：
Given a string containing just the characters'(',')','{','}','['and']', determine if the input string is valid. The brackets must close in the correct 阅读全文