https://leetcode-cn.com/problems/valid-parentheses/

    1. class Solution {
    2.     public boolean isValid(String s) {
    3.         LinkedList<Character> stack = new LinkedList<>();
    4.         // 遍历字符串中所有字符，依次判断
    5.         for (int i = 0; i < s.length(); i++) {
    6.             char c = s.charAt(i);
    7.             // 判断当前是左/右括号
    8.             if (c == '(') {
    9.                 stack.push(')');
    10.             } else if (c == '[') {
    11.                 stack.push(']');
    12.             } else if (c == '{') {
    13.                 stack.push('}');
    14.             } else {
    15.                 if (stack.isEmpty() || stack.pop() != c) return false;
    16.             }
    17.         }
    18.         return stack.isEmpty();
    19.     }
    20. }