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.
括号匹配的问题，使用栈解决。（注意，访问栈元素时要先判断栈是否为空）
C++实现代码如下：
#include<iostream> #include<string> #include<stack> using namespace std; class Solution { public: bool isValid(string s) { size_t index=0; stack<char> ss; while(index<s.length()) { char c; switch(s[index]) { case ‘(‘ : case ‘[‘ : case ‘{‘ : ss.push(s[index]); break; case ‘)‘ : if(ss.empty()) return false; c=ss.top(); if(c!=‘(‘) return false; ss.pop(); break; case ‘]‘ : if(ss.empty()) return false; c=ss.top(); if(c!=‘[‘) return false; ss.pop(); break; case ‘}‘ : if(ss.empty()) return false; c=ss.top(); if(c!=‘{‘) return false; ss.pop(); break; default: return false; } index++; } if(index==s.length()&&ss.empty()) return true; return false; } }; int main() { string str="]"; Solution s; cout<<s.isValid(str)<<endl; }
运行结果：
原文：http://www.cnblogs.com/wuchanming/p/4098102.html