leetcode[20]Valid Parentheses

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.

class Solution {
public:
    bool isValid(string s) {
       if(s.size()%2)return false;
       stack<char> stackS;
       for(int i=0;i<s.size();i++)
       {
           if(s[i]=='('||s[i]=='['||s[i]=='{')
           stackS.push(s[i]);
           if(s[i]==')'||s[i]==']'||s[i]=='}')
           {
               if(!stackS.empty())
               {
                    if(((stackS.top()=='(')&&(s[i]!=')'))||((stackS.top()=='[')&&(s[i]!=']'))||((stackS.top()=='{')&&(s[i]!='}')))
                    {
                        stackS.pop();
                        return false;
                    }
                        stackS.pop();
               }
               else
                  return false;
           }
       }
       if(stackS.empty())return true;
       else return false;
    }
};