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A working implementation of elimination/trial and error solver

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This commit is contained in:
Ray Miller 2010-07-24 14:16:52 +01:00
parent 5a74507c79
commit 3c2298127c
1 changed files with 80 additions and 17 deletions
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97
src/ray1729/clojure/sudoku/core.clj
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@ -29,9 +29,7 @@
col-map (into {} (for [ps (partition 3 cols) e ps] [e ps]))]
(for [row (row-map r) col (col-map c)] (str row col))))
(defn units [s] (vector (row-keys s) (col-keys s) (box-keys s)))
(defn peers [s] (disj (into #{} (apply concat (units s))) s))
(defn peers [s] (disj (into #{} (concat (row-keys s) (col-keys s) (box-keys s))) s))
(declare assign)
(declare eliminate)
@ -58,24 +56,27 @@
(defn solved? [grid]
(every? #(= 1 (count %)) (vals grid)))
(defn try-assign [grid cell value]
(ekit/with-handler
(assign grid cell value)
(ekit/handle *inconsistent-grid* [] nil)))
(defn try-eliminate [grid cell value]
(ekit/with-handler
(eliminate grid cell value)
(ekit/handle *inconsistent-grid* [] nil)))
(defn solve [grid]
(if (solved? grid)
grid
(let [cell (first (filter #(> (count (grid %)) 1) (keys grid)))
candidates (grid cell)
candidate (first candidates)]
(ekit/with-handler
(do
(println (str "Trying " cell "=" candidate))
(recur (assign grid cell candidate)))
(ekit/handle *inconsistent-grid* []
(if (next candidates)
(do (println (str "Trying next candidate for " cell))
(recur (eliminate grid cell candidate)))
(ekit/do-not-handle)))))))
(when grid
(if (solved? grid)
grid
(let [cell (first (filter #(> (count (grid %)) 1) (keys grid)))
value (first (grid cell))]
(or (solve (try-assign grid cell value)) (solve (try-eliminate grid cell value)))))))
(comment
;; This is a trivial puzzle: it is solved by the initial assignment
(def g1 (parse-grid
"003020600
900305001
@ -87,5 +88,67 @@
800203009
005010300"))
(solved? g1)
;;=> true
(def g2 (parse-grid "400000805030000000000700000020000060000080400000010000000603070500200000104000000"))
(print-grid g2)
;; ...4..... 1....67.9 12...67.9 | 1.3.....9 .23..6..9 12...6..9 | .......8. 123.....9 ....5....
;; .2...6789 ..3...... 12..56789 | 1..45..89 .2.456..9 12.456.89 | 12...67.9 12.4....9 12.4.67.9
;; .2...6.89 1...56.89 12..56.89 | ......7.. .23456..9 12.456.89 | 123..6..9 1234....9 1234.6..9
;; ------------------------------+-------------------------------+------------------------------
;; ..3...789 .2....... 1.3.5.789 | ..345...9 ..345.7.9 ...45.7.9 | 1.3.5.7.9 .....6... 1.3...789
;; ..3..67.9 1...567.9 1.3.567.9 | ..3.5...9 .......8. .2..567.9 | ...4..... 123.5...9 123...7.9
;; ..3..6789 ...456789 ..3.56789 | ..345...9 1........ .2.4567.9 | .23.5.7.9 .23.5..89 .23...789
;; ------------------------------+-------------------------------+------------------------------
;; .2.....89 .......89 .2.....89 | .....6... ...45...9 ..3...... | 12..5...9 ......7.. 12.4...89
;; ....5.... .....6789 ..3..6789 | .2....... ...4..7.9 1..4..789 | 1.3..6..9 1.34...89 1.34.6.89
;; 1........ .....6789 ...4..... | ....5..89 ....5.7.9 ....5.789 | .23.56..9 .23.5..89 .23..6.89
;; More tricky...
(solved? g2)
;;=> false
(def s (solve g2))
(solved? s)
;;=> true
(print-grid s)
;; ...4..... 1........ ......7.. | ..3...... .....6... ........9 | .......8. .2....... ....5....
;; .....6... ..3...... .2....... | 1........ ....5.... .......8. | ........9 ...4..... ......7..
;; ........9 ....5.... .......8. | ......7.. .2....... ...4..... | ..3...... 1........ .....6...
;; ------------------------------+-------------------------------+------------------------------
;; .......8. .2....... ....5.... | ...4..... ..3...... ......7.. | 1........ .....6... ........9
;; ......7.. ........9 1........ | ....5.... .......8. .....6... | ...4..... ..3...... .2.......
;; ..3...... ...4..... .....6... | ........9 1........ .2....... | ......7.. ....5.... .......8.
;; ------------------------------+-------------------------------+------------------------------
;; .2....... .......8. ........9 | .....6... ...4..... ..3...... | ....5.... ......7.. 1........
;; ....5.... ......7.. ..3...... | .2....... ........9 1........ | .....6... .......8. ...4.....
;; 1........ .....6... ...4..... | .......8. ......7.. ....5.... | .2....... ........9 ..3......
(def g3 (parse-grid
"008601000
600000003
000048506
040000600
780020091
001000030
109870000
200000007
000209100"))
(print-grid (solve g3))
;; ...4..... ..3...... .......8. | .....6... ....5.... 1........ | .2....... ......7.. ........9
;; .....6... 1........ ....5.... | ......7.. ........9 .2....... | .......8. ...4..... ..3......
;; ........9 .2....... ......7.. | ..3...... ...4..... .......8. | ....5.... 1........ .....6...
;; ------------------------------+-------------------------------+------------------------------
;; ..3...... ...4..... .2....... | ........9 1........ ......7.. | .....6... ....5.... .......8.
;; ......7.. .......8. .....6... | ....5.... .2....... ..3...... | ...4..... ........9 1........
;; ....5.... ........9 1........ | ...4..... .......8. .....6... | ......7.. ..3...... .2.......
;; ------------------------------+-------------------------------+------------------------------
;; 1........ .....6... ........9 | .......8. ......7.. ....5.... | ..3...... .2....... ...4.....
;; .2....... ....5.... ..3...... | 1........ .....6... ...4..... | ........9 .......8. ......7..
;; .......8. ......7.. ...4..... | .2....... ..3...... ........9 | 1........ .....6... ....5....
)