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.
至少见过3次这个题目了。栈的简单应用
class Solution { public: bool judge(char a, char b) { if (a == ‘(‘ && b == ‘)‘) return true; else if (a == ‘[‘ && b == ‘]‘) return true; else if (a == ‘{‘ && b == ‘}‘) return true; return false; } bool isValid(string s) { stack <char> st; char c; for (int i = 0; i < s.size(); ++i) { if (!st.empty()) { c = st.top(); if (judge(c, s[i])) st.pop(); else st.push(s[i]); } else st.push(s[i]); } if (st.empty()) return true; return false; } };
原文：http://www.cnblogs.com/pk28/p/7200142.html