1 files changed, 46 insertions, 0 deletions
diff --git a/day11.lisp b/day11.lisp
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+(defun read-lines (filespec)
+  (with-open-file (stream filespec)
+    (loop for line = (read-line stream nil)
+          while line
+          collect line)))
+
+(defun empty-rows (lines)
+  (loop for line in lines
+        collect (every (lambda (c) (equal c #\.)) line)))
+
+(defun empty-cols (lines)
+  (loop for i below (length (first lines))
+        collect (every (lambda (line) (equal (aref line i) #\.)) lines)))
+
+(defun galaxies-coords (lines erows ecols eincrement)
+  (loop for i = 0 then (+ i (if erow eincrement 1))
+        for erow in erows
+        for line in lines
+        append (loop for j = 0 then (+ j (if ecol eincrement 1))
+                     for ecol in ecols
+                     for c across line
+                     if (equal c #\#)
+                       collect (cons i j))))
+
+(defun solve (filespec eincrement)
+  (let* ((lines (read-lines filespec))
+         (erows (empty-rows lines))
+         (ecols (empty-cols lines))
+         (coords (galaxies-coords lines erows ecols eincrement)))
+    (loop for coord in coords
+          for rem on (cdr coords)
+          while rem
+          sum (loop for other in rem
+                    sum (+ (abs (- (car coord) (car other)))
+                           (abs (- (cdr coord) (cdr other))))))))
+
+(defun solve1 (filespec)
+  (solve filespec 2))
+
+(defun solve2 (filespec)
+  (solve filespec 1000000))
+
+(print (solve1 "data/11/example.txt"))  ; 374
+(print (solve1 "data/11/input.txt"))    ; 9563821
+(print (solve2 "data/11/example.txt"))  ; 82000210
+(print (solve2 "data/11/input.txt"))    ; 827009909817