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.
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判断括号嵌套是否合法,
思路:利用栈,在加入栈前,依次判断栈首元素 是否 和待加入元素 匹配,
如果匹配,直接弹出栈首元素
代码:
class Solution { public: bool isValid(string s) { stack<char> stac; if(s.empty()) return true; for(int i = 0;i<(int)s.size();i++){ if(stac.empty()){ stac.push(s[i]); continue; } if(‘[‘==stac.top() && ‘]‘==s[i]) stac.pop(); else if(‘{‘==stac.top() && ‘}‘==s[i]) stac.pop(); else if(‘(‘==stac.top() && ‘)‘==s[i]) stac.pop(); else stac.push(s[i]); } return stac.empty()? true:false; } };
原文：http://www.cnblogs.com/li-daphne/p/5608063.html