码迷,mamicode.com
首页 > 其他好文 > 详细

【LeetCode】20. Valid Parentheses

时间:2019-10-04 23:20:46      阅读:186      评论:0      收藏:0      [点我收藏+]

标签:new   difficult   diff   des   else   problems   ||   span   strong   

Difficulty:easy

 More:【目录】LeetCode Java实现

Description

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

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

An input string is valid if:

  1. Open brackets must be closed by the same type of brackets.
  2. Open brackets must be closed in the correct order.

Note that an empty string is also considered valid.

Example 1:

Input: "()"
Output: true

Example 2:

Input: "()[]{}"
Output: true

Example 3:

Input: "(]"
Output: false

Example 4:

Input: "([)]"
Output: false

Example 5:

Input: "{[]}"
Output: true

Intuition

Using a stack.

 

Solution

    public boolean isValid(String s) {
        if(s==null)
            return false;
        Stack<Character> stk = new Stack<Character>();
        for(Character c : s.toCharArray()){
            if(c==‘(‘)
                stk.push(‘)‘);
            else if(c==‘[‘)
                stk.push(‘]‘);
            else if(c==‘{‘)
                stk.push(‘}‘);
            else if(stk.isEmpty() || stk.pop()!=c)
                return false;
        }
        return stk.isEmpty();
    }

  

Complexity

Time complexity : O(n)

Space complexity : O(n)

 

 More:【目录】LeetCode Java实现

 

【LeetCode】20. Valid Parentheses

标签:new   difficult   diff   des   else   problems   ||   span   strong   

原文地址:https://www.cnblogs.com/yongh/p/11623339.html

(0)
(0)
   
举报
评论 一句话评论(0
登录后才能评论!
© 2014 mamicode.com 版权所有  联系我们:gaon5@hotmail.com
迷上了代码!