Clojure: how to merge several sorted vectors of vectors into common structure? -

need help. stuck on intuitively simple task.

i have few vectors of vectors. first element of each of sub-vectors numeric key. parent vectors sorted these keys. example:

[[1 b] [3 c d] [4 f d] .... ]   [[1 aa bb] [2 cc dd] [3 ww qq] [5 f]... ]  [[3 ccc ddd] [4 fff ddd] ...] 

need clarify key values in nested vectors may missing, sorting order guaranteed.

i need merge of these vectors unified structure numeric keys. need now, key missed in original vector or vectors.

like this:

[ [[1 b][1 aa bb][]] [[][2 cc dd]] [[3 c d][3 ww qq][3 ccc ddd]] [[4 f d][][4 fff dd]]...] 

you can break problem down 2 parts:

1) unique keys in sorted order

2) each unique key, iterate through list of vectors, , output either entry key, or empty list if missing

to unique keys, pull out keys lists, concat them 1 big list, , put them sorted-set:

(into    (sorted-set)      (apply concat        (for [vector vectors]          (map first vector)))) 

if start list of vectors of:

(def vectors   [[[1 'a 'b] [3 'c 'd] [4 'f 'd]]     [[1 'aa 'bb] [2 'cc 'dd] [3 'ww 'qq] [5 'f]]    [[3 'ccc 'ddd] [4 'fff 'ddd]]]) 

then sorted set of:

=> #{1 2 3 4 5} 

so far good. each key in sorted set need iterate through vectors, , entry key, or empty list if it's missing. can using 2 'for' forms , 'some' find entry (if present)

(for [k #{1 2 3 4 5}]   (for [vector vectors]     (or (some #(when (= (first %) k) %) vector )         []))) 

this yields:

=> (([1 b] [1 aa bb] []) ([] [2 cc dd] []) ([3 c d] [3 ww qq] [3 ccc ddd]) ([4 f d] [] [4 fff ddd]) ([] [5 f] [])) 

which think want. (if need vectors , not lists, use "(into [] ...)" in appropriate places.)

putting together, get:

(defn unify-vectors [vectors]    (for [k (into (sorted-set)                  (apply concat                        (for [vector vectors]                          (map first vector))))]     (for [vector vectors]       (or (some #(when (= (first %) k) %) vector)           []))))  (unify-vectors  [[[1 'a 'b] [3 'c 'd] [4 'f 'd]]    [[1 'aa 'bb] [2 'cc 'dd] [3 'ww 'qq] [5 'f]]   [[3 'ccc 'ddd] [4 'fff 'ddd]]])  => (([1 b] [1 aa bb] []) ([] [2 cc dd] []) ([3 c d] [3 ww qq] [3 ccc ddd]) ([4 f d] [] [4 fff ddd]) ([] [5 f] []))