8queens-loco.clj

;; depends on [loco "0.3.1"]
(ns loco-playground.core
  (:require [loco.core :refer :all]
            [loco.constraints :refer :all]))

(def queens-model
    (conj 
          ;; Variables [:x i] [:y i] para la posición de la reina i-ésima
          (mapcat #(vector ($in [:x %] 0 7) ($in [:y %] 0 7)) (range 8))
          ;; Todas las filas deben ser distintas
          ($distinct (map (partial vector :x) (range 8)))
          ;; Todas las columnas deben ser distintas
          ($distinct (map (partial vector :y) (range 8)))
          ;; Todas las diagonales deben ser distintas
          ($distinct (map #($- [:x %] [:y %]) (range 8)))
          ;; Toas las contra-diagonales deben ser distintas
          ($distinct (map #($+ [:x %] [:y %]) (range 8)))))

(defn place-queens [queens]
  (let [board (vec (map (fn [_] (vec (take 8 (repeat 0)))) (range 8)))]
    (->> (range 8)
         (reduce (fn [b i] (let [x (queens [:x i]) y (queens [:y i])]
                             (assoc-in b [x y] 1)))
                 board))))

;; Busco una solución y la pinto
(clojure.pprint/pprint (place-queens (solution queens-model)))