[英]reversing hash map in clojure
I've hash-map in clojure: 我在clojure中使用哈希映射:
{"key1" "value1"} {"key2" "value2"} {"key3" "value1"}
and i need to convert it into hash map of 我需要将其转换为哈希映射
{"value1" {"key1" "key3"}} {"value2" {"key2"}}
Any clojure way of doing this? 这样做的任何clojure方式?
clojure.set/map-invert will not work as if it overrides repeated values. clojure.set / map-invert不会像重写值一样工作。
(def m {"key1" "value1" "key2" "value2" "key3" "value1"})
(let [g (group-by val m)
vals (map #(map first %) (vals g))]
(zipmap (keys g) vals))
;;=> {"value2" ("key2"), "value1" ("key1" "key3")}
Give this a try: 尝试一下:
(def m {"key1" "value1" "key2" "value2" "key3" "value1"})
(reduce (fn [a x] (assoc a (second x) (conj (a (second x)) (first x)))) {} m)
=> {"value2" ("key2"), "value1" ("key3" "key1")}
Notice that the (possibly) repeated values end up in a list. 请注意,(可能)重复的值最终会出现在列表中。 Or, as suggested by @A.Webb in the comments, the above can be concisely written like this: 或者,正如@ A.Webb在评论中所建议的那样,上面的内容可以简洁地写成:
(reduce (fn [a [k v]] (update-in a [v] conj k)) {} m)
=> {"value2" ("key2"), "value1" ("key3" "key1")}
尝试以下操作,我没有REPL进行测试,它可能与原始答案略有不同,但是,您可以使用它来获得您想要的。
(group-by #(val (first %)) {"key1" "value1"} {"key2" "value2"} {"key3" "value1"})
Your question is really confusing. 你的问题真的令人困惑。 First you said you have hash-map, what you actually have as example is many hash-maps or if you really mean a single hash-map then your example is incorrect as it should be {"key1" "value1" "key2" "value2" "key3" "value1"}
. 首先你说你有哈希映射,你实际上有什么例子是很多哈希映射,或者如果你真的是一个哈希映射,那么你的例子是不正确的,因为它应该是{"key1" "value1" "key2" "value2" "key3" "value1"}
。 Second, the required output is weird in the sense that the values in the hash-map are represented as maps themselves but the last value is just a single value in a hash-map which is obviously not possible, so I guess you mean the values are set (not map) as {"value1" #{"key1" "key3"}} {"value2" #{"key2"}}
其次,所需的输出很奇怪,哈希映射中的值表示为映射本身,但最后一个值只是哈希映射中的单个值,这显然是不可能的,所以我猜你的意思是值设置(不是地图)为{"value1" #{"key1" "key3"}} {"value2" #{"key2"}}
Based on all these assumptions one possible solution would be: 基于所有这些假设,一种可能的解决方案是:
(->> {"key1" "value1" "key2" "value2" "key3" "value1"}
(group-by second)
(map #(-> [(%1 0) (into #{} (map first (%1 1)))]))
(into {}))
Here's another alternative: 这是另一种选择:
(def maps [{"key1" "value1"} {"key2" "value2"} {"key3" "value1"}])
(into {}
(for [[k v] (group-by #(val (first %)) maps)]
[k (apply concat (map keys v))]))
;=> {"value1" ("key1" "key3"), "value2" ("key2")}
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