class Solution {public:    int longestValidParentheses(string s) {         stack<int> mstack;		 char cbefore;         int count = 0;		 if(s.empty())		  return 0;		 		 for(int i=0; i<s.size(); i++)		 {            		     bool ret;						 CountTotal(mstack,count);			 if(mstack.empty())			 {			    if(count!=0)			    {					mstack.push(count);					mstack.push(‘a‘);					count =0;				}			    				mstack.push(s[i]);								continue;			 }                        ret = CheckValidParentheses(mstack.top(),s[i]);			 if(ret == false)			 {  				if(count!=0)			    {					mstack.push(count);					mstack.push(‘a‘);					count =0;				}                  mstack.push(s[i]);	  			 }			 else			 {			     mstack.pop();			     count++;				 mstack.push(count);				 mstack.push(‘a‘);				 count =0;				 						 }			 		 }	    CountTotal(mstack,count);	  int maxcount = count;	  count =0;	  while(!mstack.empty())	  {          if(mstack.top() != ‘a‘)		  {             mstack.pop();			 if(count > maxcount)			 	maxcount = count;			 count =0;			 continue;		  };		  		  mstack.pop();		  count+=mstack.top();		  mstack.pop();	  }      if(count > maxcount)		maxcount = count;	   return maxcount*2;		         }	bool CheckValidParentheses(char a,char b)	{        if(a == ‘(‘ && b == ‘)‘)		 return true;		return false;	}	void CountTotal(stack<int>& mstack,int& count)	{	  		while(1)		{    		  if(mstack.empty())		  	return;		  if(mstack.top() != ‘a‘)		  	return;		  		  mstack.pop();		  count+=mstack.top();		  mstack.pop();		}	}};