CODEWITHSUNDEEP
clojure
ruby_object
ruby_object

Reputation: 1266

How do I create a map of string indexes in Clojure?

I want to create a map where the keys are characters in the string and the values of each key are lists of positions of given character in the string.

Upvotes: 0

Views: 246

Answers (2)

leetwinski
leetwinski

Reputation: 17859

a bit shorter variant:

(defn process [^String s]
  (group-by #(.charAt s %) (range (count s))))


user> (process "asdasdasd")
;;=> {\a [0 3 6], \s [1 4 7], \d [2 5 8]}

notice that indices here are sorted

Upvotes: 6

Scott
Scott

Reputation: 1688

I am sure there are several solutions for this. My first thought was use map-indexed to get a list of [index character] then reduce the collection in to a map. 

(defn char-index-map [sz]
  (reduce
   (fn [accum [i ch]]
     (update accum ch conj i))
   {}
   (map-indexed vector sz)))


(char-index-map "aabcab")

;;=> {\a (4 1 0), \b (5 2), \c (3)}

Upvotes: 4

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