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<char> 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 };