各位小伙伴们，2020还有最后两周就要结束了，很多公司陆陆续续也都开始了年会的准备工作。而年会上，大家最期待的节目，无疑就是抽奖了。
有一天，领导告诉你 “小胖儿，公司马上开年会了，你给我们写个抽奖程序吧”。随后，你默默地打开了Eclipse，开始写Math.random()。
今天，风哥告诉你，抽奖这事儿，其实不用这么麻烦，可以考虑使用Redis的set集合。
我们都知道，set的两大特点，去重和无序。同样，Redis的set也满足这两个特点。
先来看看Redis的set提供给我们哪些用法（可以发现，set相关的命令大多以s开头）。
127.0.0.1:6379> help @set
SADD key member [member ...]
summary: Add one or more members to a set
since: 1.0.0
SCARD key
summary: Get the number of members in a set
since: 1.0.0
SDIFF key [key ...]
summary: Subtract multiple sets
since: 1.0.0
SDIFFSTORE destination key [key ...]
summary: Subtract multiple sets and store the resulting set in a key
since: 1.0.0
SINTER key [key ...]
summary: Intersect multiple sets
since: 1.0.0
SINTERSTORE destination key [key ...]
summary: Intersect multiple sets and store the resulting set in a key
since: 1.0.0
SISMEMBER key member
summary: Determine if a given value is a member of a set
since: 1.0.0
SMEMBERS key
summary: Get all the members in a set
since: 1.0.0
SMOVE source destination member
summary: Move a member from one set to another
since: 1.0.0
SPOP key [count]
summary: Remove and return one or multiple random members from a set
since: 1.0.0
SRANDMEMBER key [count]
summary: Get one or multiple random members from a set
since: 1.0.0
SREM key member [member ...]
summary: Remove one or more members from a set
since: 1.0.0
SSCAN key cursor [MATCH pattern] [COUNT count]
summary: Incrementally iterate Set elements
since: 2.8.0
SUNION key [key ...]
summary: Add multiple sets
since: 1.0.0
SUNIONSTORE destination key [key ...]
summary: Add multiple sets and store the resulting set in a key
since: 1.0.0我们挑几个常用的看一下。
127.0.0.1:6379> SADD k1 a a b b c d //在名为k1的集合中添加abcd四个元素
(integer) 4
127.0.0.1:6379> SADD k2 b c d e
(integer) 4
127.0.0.1:6379> SCARD k1 //列出集合的大小
(integer) 4
127.0.0.1:6379> SMEMBERS k1 //列出集合中所有元素，可以看出“去重且乱序”的
1) "c"
2) "a"
3) "d"
4) "b"
127.0.0.1:6379> SISMEMBER k1 a //集合k1是否包含a
(integer) 1
127.0.0.1:6379> SISMEMBER k1 aa
(integer) 0
127.0.0.1:6379> sdiff k1 k2 //集合k1和k2的差异，k1,k2是有顺序的（k1-k2）
1) "a"
127.0.0.1:6379> sdiff k2 k1
1) "e"
127.0.0.1:6379> SUNION k1 k2 // 并集
1) "a"
2) "d"
3) "b"
4) "c"
5) "e"
127.0.0.1:6379> SINTER k1 k2 //交集
1) "c"
2) "d"
3) "b"
127.0.0.1:6379> SRANDMEMBER k1 //从集合中随机取出（get）一个元素
"c"
127.0.0.1:6379> SRANDMEMBER k1
"b"
127.0.0.1:6379> SRANDMEMBER k1 3 //从集合中随机（这不废话吗，反正set也是无序的）取出3个元素
1) "c"
2) "d"
3) "b"
127.0.0.1:6379> SRANDMEMBER k1 3
1) "a"
2) "d"
3) "b"
127.0.0.1:6379> SPOP k1 3 //从集合中随机取出（remove）3个元素
1) "d"
2) "a"
3) "b"
127.0.0.1:6379> SPOP k1 2
1) "c"看到这你可能已经发现了，抽奖这事儿，用 SRANDMEMBER 或者 SPOP 就能搞定。
1. 奖品数>抽奖人数
假设3个人的公司，准备了5份奖品，即可以重复中奖。
127.0.0.1:6379> sadd lotteryList tom jerry tony
(integer) 3
127.0.0.1:6379> SRANDMEMBER lotteryList -5 //如果为负数，会首先满足返回元素个数，可能会有重复
1) "tom"
2) "jerry"
3) "tony"
4) "jerry"
5) "jerry"2. 奖品数<抽奖人数
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127.0.0.1:6379> sadd lottoryList tom jerry jack tony lucy lily poly kevin
(integer) 8
127.0.0.1:6379> spop lottoryList 3 //三等奖
1) "jerry"
2) "jack"
3) "lily"
127.0.0.1:6379> spop lottoryList 2 //二等奖
1) "kevin"
2) "poly"
127.0.0.1:6379> spop lottoryList 1 //一等奖
1) "tony"总结
我们稍微总结一下，类似抽奖这种简单随机场景，可以根据实际情况，考虑另一种思路，即使用Redis的 SRANDMEMBER 或者 spop 来实现。
好了，本次分享就是这样，我们下次讲 sorted_set，希望你能有收获。
