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.
一般匹配的问题需要用到栈或者队列
代码如下：
class Solution { public: bool isValid(string s) { stack<char> st; for(int i=0;i<s.length();i++){ if(s[i] == ']' || s[i] == '}' || s[i] == ')'){ if(st.empty()){ return false; }else{ char c = st.top(); st.pop(); if((s[i] == ']' && c != '[')||(s[i] == '}' && c != '{') || (s[i] == ')' && c != '(')) return false; } } else st.push(s[i]); } return st.empty(); } };
