Given a string containing just the characters '(' and ')', find the length of the longest valid (well-formed) parentheses substring.
For "(()", the longest valid parentheses substring is "()", which has length = 2.
Another example is ")()())", where the longest valid parentheses substring is "()()", which has length = 4.
参考：http://www.cnblogs.com/easonliu/p/3637429.html
C++ 代码实现：
#include<iostream> #include<string> #include<stack> using namespace std; class Solution { public: int longestValidParentheses(string s) { stack<int> st; if(s.empty()) return 0; bool a[s.length()]; size_t i; for(i=0; i<s.length(); i++) { if(s[i]=='(') { //还没有匹配的都设置为false a[i]=false; st.push(i); } else if(!st.empty()&&s[i]==')') { //每次匹配设置两个为true a[i]=true; a[st.top()]=true; st.pop(); } else a[i]=false; } int max=0; int count=0; for(i=0; i<s.length(); i++) { if(a[i]) count++; else count=0; if(count>max) max=count; } return max; } }; int main() { Solution s; string str="(()"; cout<<s.longestValidParentheses(str)<<endl; }
