Valid Parentheses

Description

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

The brackets must close in the correct order, "()" and "()[]{}" are all valid but "(]" and "([)]" are not.

给出包含三种括号的字符串,验证括号是否左右匹配

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系统安装

系统: raspbian
工具(二选一):

  1. 将SD卡格式化成exFat格式
  2. 使用Etcher或者Win32DiskImager将下载的raspbian系统镜像(img文件)写入SD卡

写入完成之后就相当于系统安装完成了。这时候SD卡被分成两个区,有一个区是在windows下无法识别,不用理会。

这时候如果直接将SD卡插入树莓派,会发现“无法启动”。显示屏没信号,在路由器里找到树莓派的IP也无法用ssh登录。

我安装的时候就是踩到这个坑。以为安装失败,反复装了好几次,就差把SD卡写穿了。

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4Sum

Description

Given an array S of n integers, are there elements a, b, c, and d in S such that a + b + c + d = target? Find all unique quadruplets in the array which gives the sum of target.

Note: The solution set must not contain duplicate quadruplets.

For example, given array S = [1, 0, -1, 0, -2, 2], and target = 0.

A solution set is:
[
  [-1,  0, 0, 1],
  [-2, -1, 1, 2],
  [-2,  0, 0, 2]
]

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Author's picture

SelFree

城市永远年轻,而我们终将老去

Programer

ChengDu