摘要：
Given a string containing just the characters '(' and ')', find the length of the longest valid (well-formed) parentheses substring. Example 1: Exampl 阅读全文
摘要：
We are given S, a length n string of characters from the set {'D', 'I'}. (These letters stand for "decreasing" and "increasing".) A valid permutation 阅读全文