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.

 1 public class Solution {
 2     public boolean isValid(String s) {
 3         Stack<Character> stack = new Stack<Character>();
 4         char[] c = s.toCharArray();
 5         for(int i=0;i<c.length;i++){
 6             if(stack.isEmpty() || !is(stack.peek(),c[i])){
 7                 stack.push(c[i]);
 8             }
 9             else{
10                 stack.pop();
11             }
12         }
13         return stack.isEmpty();
14     }
15     public boolean is(char a,char b){
16         if(a=='(') return b==')';
17         if(a=='{') return b=='}';
18         if(a=='[') return b==']';
19         return false;
20     }
21 }
View Code

 

posted @ 2014-02-06 05:34  krunning  阅读(94)  评论(0)    收藏  举报