1 class Solution { 2 public: 3     /** 4      * @param s A string 5      * @return whether the string is a valid parentheses 6      */ 7     bool isValidParentheses(string& s) { 8         // Write your code here 9         stack
     
       parens;10         for (int i = 0; i < (int)s.length(); i++) {11             if (s[i] == '(' || s[i] == '[' || s[i] == '{
    ')12                 parens.push(s[i]);13             else if (parens.empty() || !match(s[i], parens.top()))14                 return false;15             else parens.pop();16         }17         return parens.empty();18     }19 private:20     bool match(char s, char t) {21         if (s == ')') return t == '(';22         if (s == ']') return t == '[';23         if (s == '}') return t == '{
    ';24     }25 };