Sudoku: Difference between revisions

Content added Content deleted

Inline

@@ Line 1,834: / Line 1,834: @@
 using System.Collections.Generic;
 using System;
+using System.IO;
 namespace Sudoku {
@@ Line 1,851: / Line 1,852: @@
             GetBox(grid, row, col).IsUnequal();
-        private static (int, int) NextEmptyCell(this int[][] grid, int r, int c) =>
+        private static bool Solve(this int[][] grid, int r, int c) {
-            r < 9 && grid[r][c] != 0
+            if (r == 9)
-            ? NextEmptyCell(grid, c == 8 ? r + 1 : r, ++c % 9)
-            : (r, c);
-        private static bool Solve(this int[][] grid, int row, int col) {
-            var (r, c) = grid.NextEmptyCell(row, col);
-            if (r == 9) //finished
                 return true;
+            if (grid[r][c] != 0)
+                return grid.Solve(c == 8 ? r + 1 : r, ++c % 9);
             foreach (var i in Range(1,9)) {
                 grid[r][c] = i;
                 if (grid.Constraints(r, c) && grid.Solve(r, c))
                     return true;
-            }
+                grid[r][c] = 0;
-            grid[r][c] = 0; //backtrack
+            }
             return false;
         }
-        static void Main(string[] args) {
+        private static int[][] Parse(string input) =>
-            var grid = new string[]{
+            input
-                "970 340 060",
+            .Select((c, i) => (index: i, val: (int)c - '0'))
+            .GroupBy(id => id.index / 9).Select(grp => grp.Select(id => id.val).ToArray())
-                "861 750 000",
-                "324 168 957",
+            .ToArray();
-                "219 584 673",
-                "487 236 519",
-                "653 971 284",
-                "738 425 196",
-                "002 010 048",
-                "040 007 300" }
-                .Select(r => r.Where(c => c != ' ').Select(c => (int)c - '0').ToArray())
-                .ToArray();
+        static void Main(string[] args) {
+            //https://staffhome.ecm.uwa.edu.au/~00013890/sudoku17 format
+            var puzzle = "000028000800010000000000700000600403200004000100700000030400500000000010060000000";
+            var grid = Parse(puzzle);
             Write(grid.Solve(0, 0)
                 ? string.Join('\n', grid.Select(row=>string.Concat(row)))
@@ Line 1,892: / Line 1,888: @@
 </lang>
 Output
-<pre>975342861
+<pre>
+617328945
-861759432
+894517236
-324168957
+325946781
-219584673
+978651423
-487236519
+256834179
-653971284
+143792658
-738425196
+731489562
-592613748
+489265317
-146897325
-</pre>
+562173894</pre>
 ===“Automatic” Solution===