Valid Parentheses(括弧匹配)

class Solution {
public:
    bool isValid(string s) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        stack<char> mystack;
        int count = s.length();
        for(int i = 0;i < count;i++)
        {
            if(s[i]=='('||s[i]=='{'||s[i]=='[')
            {
                mystack.push(s[i]);
            }
            else
            {
                if(mystack.empty())
                return false;
                switch(s[i])
                {
                    case '}':if(mystack.top()!='{')
                            return false;
                            break;
                    case ']':if(mystack.top()!='[')
                            return false;
                            break;
                    case ')':if(mystack.top()!='(')
                            return false;
                            break;
                }
                mystack.pop();
            }
        }
        return mystack.empty();
    }
};