Valid Parentheses

Valid Parentheses

问题：

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.

思路：

　　经典栈的应用

我的代码：

public class Solution {
    public boolean isValid(String s) {
        if(s == null || s.length() == 0) return true;
        Stack<Character> stack = new Stack<Character>();
        for(int i = 0; i < s.length(); i++)
        {
            char c = s.charAt(i);
            if(isRight(c))
            {
                if(stack.isEmpty()) return false;
                char left = stack.pop();
                if(!isMatch(left,c)) return false;
            }
            else
            {
                stack.push(c);
            }
        }
        return stack.isEmpty();
    }
    public boolean isMatch(char left, char right)
    {
        if((left=='('&&right==')')||(left=='['&&right==']')||(left=='{'&&right=='}'))   return true;
        return false;
    }
    public boolean isRight(char c)
    {
        if(c == ')' || c == ']' || c == '}')    return true;
        return false;
    }
}