ARTS第三十五周(2020年5月18日~24日)
Algorithm
编号 | 难度 | 题目 | 我的解答 | 执行用时 | 内存消耗 | 排名 | 备注 |
---|---|---|---|---|---|---|---|
237 | 简单 | 删除链表中的节点 | 200524-1.cpp | 20 ms | 8 MB | 23.90% | |
238 | 中等 | 除自身以外数组的乘积 | 200524-2.cpp | 24 ms | 16.1 MB | 43.33% |
Review
1. C++中实现具有多态性的赋值
分享链接:How to Assign Derived Classes in C++
C++中,要让对象的多态性生效,就需要使用指针或是引用。也因此,在对象的直接赋值过程中,多态性就很难实现。但如果使用的是对象引用,进行赋值,如何实现多态性呢?该问题的具体代码描述如下:
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这篇教程从基于dynamic_cast
的基本实现出发,一步步改善代码,最终使其很方便地定义此类多态性的赋值语法。
Tip
1. 列举Linux用户
过去通常使用cat /etc/passwd
来列举当前系统中都有哪些用户。本周学到一个更好用的新命令:
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其结果大致为如下格式:
UID USER PROC PWD-LOCK PWD-DENY LAST-LOGIN GECOS
0 root 159 Apr22/21:49 root
1 bin 0 bin
2 daemon 0 daemon
3 adm 0 adm
4 lp 0 lp
5 sync 0 sync
6 shutdown 0 May18/12:12 shutdown
7 halt 0 halt
8 mail 0 Mail program user
9 news 0 news
10 uucp 0 uucp
11 operator 0 operator
13 man 0 System user; man
14 postmaster 0 Postmaster user
16 cron 0 added by portage for cronbase
21 ftp 0 File Transfer Protocol server user
22 sshd 0 User for ssh
45 mpd 0 A user for music player daemon (mpd)
60 mysql 1 MySQL program user
61 avahi 0 user for avahi
70 postgres 0 added by portage for postgresql
81 apache 3 added by portage for apache
88 nullmail 0 added by portage for nullmailer
101 messagebus 1 System user; messagebus
102 polkitd 1 System user; polkitd
123 ntp 0 added by portage for ntp
191 systemd-journal-remote 0 System user; systemd-journal-remote
192 systemd-network 0 System user; systemd-network
193 systemd-resolve 0 System user; systemd-resolve
194 systemd-coredump 0 System user; systemd-coredump
195 systemd-timesync 1 System user; systemd-timesync
250 portage 0 portage
335 epmd 0 User for Erlang Protmapper Daemon
990 mongodb 0 added by portage for mongodb
991 nginx 0 added by portage for nginx
992 fetchmail 0 added by portage for fetchmail
993 tcpdump 0 added by portage for tcpdump
994 arpwatch 0 added by portage for arpwatch
995 openvpn 0 User for net-vpn/openvpn
996 gdm 31 added by portage for gdm
997 geoclue 1 added by portage for geoclue
998 dhcp 0 added by portage for dhcp
999 colord 1 added by portage for colord
1000 yanll 139 May18/12:13
65534 nobody 0 nobody
Share
1. 直观掌握内存与指针的概念
分享链接:[c][explained] Demystifying Pointers — What are they?
在C语言中,最大的难点无疑是指针,理解其概念,包括其内存布局,对于后续计算机语言的学习和提升,是重要的。这个视频能够帮助初学者直观地进行理解。
2. 用R语言绘制各类图形
分享链接:R Graph Gallery
这个网站汇集了各类R语言实现的图表,对于想要以炫酷形式展示数据的,不妨经常在这里进行浏览,并研究一下相关的实现包及其用法。