程序员子悠 · 好记性不如烂笔头

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Algorithm

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1. Description

Given a string containing just the characters '(', ')', '{', '}', '[' and ']', determine if the input string is valid.

An input string is valid if:

Open brackets must be closed by the same type of brackets.

Open brackets must be closed in the correct order.

Note that an empty string is also considered valid.

2. My Solution

package com.silence.arts.leetcode.list;


import java.util.*;

/**
 * <br>
 * <b>Function：</b><br>
 * <b>Author：</b>@author Silence<br>
 * <b>Date：</b>2018-11-25 16:49<br>
 * <b>Desc：</b>无<br>
 */
public class ValidParentheses_20 {

    /**
     *
     * @param s
     * @return
     */
    public static boolean isValid(String s) {
        if (null != s && s.length() > 0) {
            Map<String, String> map = new HashMap<>();
            map.put(")", "(");
            map.put("]", "[");
            map.put("}", "{");
            Stack<String> stack = new Stack<>();
            for (int i = 0; i < s.length(); i++) {
                String val = String.valueOf(s.charAt(i));
                //if (!map.containsKey(val)) {
                if (val.equals("(") || val.equals("[") || val.equals("{")) {
                    stack.push(val);
                } else if (stack.size() <= 0 || !map.get(val).equals(stack.pop())) {
                    return false;
                }
            }
            //stack needs empty
            return stack.size() <= 0;
        }
        return true;
    }

    public static void main(String[] args) {
        System.out.println(isValid(""));
    }
}

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One more thing

• Personal Medium Home Page: https://medium.com/@zhuxiang134
• Personal Website: https://zxsilence.cn/