题解 | #有效括号序列#

import java.util.*;


public class Solution {
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     * 
     * @param s string字符串 
     * @return bool布尔型
     */
    public boolean isValid (String s) {
        // write code here
        Stack<Character> stack = new Stack<>();
        for(int i = 0; i < s.length(); i++){
            char c = s.charAt(i);
            if(stack.isEmpty()){
                stack.push(c);
            }else if(stack.peek()=='('&&c==')'){
                stack.pop();
            }else if(stack.peek()=='['&&c==']'){
                stack.pop();
            }else if(stack.peek()=='{'&&c=='}'){
                stack.pop();
            }else{
                stack.push(c);
            }
        }
        return stack.isEmpty();
    }
}