Valid Parentheses

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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.

用stack做。恩先复习下stack的用法。。。

public class Solution {    public boolean isValid(String s) {        Stack<Character> stack=new Stack<Character>();        for(int i=0;i<s.length();i++){            char c=s.charAt(i);            if(c=='('||c=='{'||c=='[')            stack.push(c);            else if(c==')'||c=='}'||c==']'){                if(stack.size()==0)                return false;                            char cpop=stack.pop();                if(c=='}'&&cpop=='{')                continue;                if(c==')'&&cpop=='(')                continue;                if(c==']'&&cpop=='[')                continue;                else return false;             }            }            return stack.size()==0;    }}

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