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

        char[] array = s.toCharArray();
        if (array.length % 2 != 0||array[0]=='}'||array[0]==']'||array[0]==')') {
            return false;
        }
        ArrayDeque<Character> stack = new ArrayDeque<>();
        int i = 0;
        while (i < array.length) {
            if (array[i] == '{' || array[i] == '[' || array[i] == '(') {
                stack.push(array[i]);
                i++;
                continue;
            }
            if (array[i] == '}') {
                if (stack.peek()!=null&&stack.peek() == '{') {
                    stack.pop();
                    i++;
                    continue;
                }
                return false;
            }
            if (array[i] == ']') {
                if (stack.peek()!=null&&stack.peek() == '[') {
                    stack.pop();
                    i++;
                    continue;
                }
                return false;
            }
            if (array[i] == ')') {
                if (stack.peek()!=null&&stack.peek() == '(') {
                    stack.pop();
                    i++;
                    continue;
                }
                return false;
            }
        }
        return stack.isEmpty();
    }
}