题目描述：
Given a string containing just the characters ‘(‘, ‘)‘, ‘{‘, ‘}‘, ‘[‘ and ‘]‘, determine if the input string is valid.
The brackets must close in the correct order, "()" and "()[]{}" are all valid but "(]" and "([)]" are not.
典型的用stack解决的问题。
solution：
bool isValid(string s) { if (s.empty() || s.size() % 2 != 0) return false; stack<char> stk; for (int i = 0;i < s.size();++i) { if(s[i] == ‘(‘ || s[i] == ‘[‘ || s[i] == ‘{‘) stk.push(s[i]); else { if (stk.empty()) return false; char ch = stk.top(); stk.pop(); if(s[i] == ‘)‘ && ch != ‘(‘) return false; if (s[i] == ‘]‘ && ch != ‘[‘) return false; if (s[i] == ‘}‘ && ch != ‘{‘) return false; } } return stk.empty(); }
如有其它解法，欢迎来稿。
原文：http://www.cnblogs.com/gattaca/p/4330010.html