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++) {
            if (stack.isEmpty() || !peer(stack.peek(), s.charAt(i))) {
                stack.push(s.charAt(i));
            } else {
                stack.pop();
            }
        }
        return stack.isEmpty() ? true : false;
    }

    private boolean peer(char c1, char c2) {
        // TODO
        boolean res = false;
        if (c1 == '{' && c2 == '}') res = true;
        if (c1 == '[' && c2 == ']') res = true;
        if (c1 == '(' && c2 == ')') res = true;
        return res;
    }

}