用stack
1 class Solution { 2 public boolean isValid(String s) { 3 Stackstack = new Stack (); 4 char[] arr = s.toCharArray(); 5 for(char c : arr) { 6 if(c == '(') { 7 stack.push(')'); 8 }else if(c == '{') { 9 stack.push('}');10 }else if(c == '[') {11 stack.push(']');12 }else if(stack.isEmpty() || stack.pop() != c) {13 return false;14 }15 }16 return stack.isEmpty();17 18 }19 }