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) {
        if (s.length() == 0 || s.length() % 2 != 0) return false;
        char firstChar = s.charAt(0);
        if (firstChar == ')' || firstChar == ']' || firstChar == '}') return false;

        Stack<Character> stack = new Stack<>();
        for (char cha : s.toCharArray()) {
            if (cha == '(' || cha == '[' || cha == '{') {
                stack.push(cha);
            } else {
                char popChar = stack.pop();
                if (cha == ')' && popChar != '(') return false;
                if (cha == ']' && popChar != '[') return false;
                if (cha == '}' && popChar != '{') return false;
            }
        }
        return stack.empty();
    }
}