Data commit

Task/Solve-a-Hopido-puzzle/Java/solve-a-hopido-puzzle.java

@@ -0,0 +1,109 @@
+import java.util.*;
+
+public class Hopido {
+
+    final static String[] board = {
+        ".00.00.",
+        "0000000",
+        "0000000",
+        ".00000.",
+        "..000..",
+        "...0..."};
+
+    final static int[][] moves = {{-3, 0}, {0, 3}, {3, 0}, {0, -3},
+    {2, 2}, {2, -2}, {-2, 2}, {-2, -2}};
+    static int[][] grid;
+    static int totalToFill;
+
+    public static void main(String[] args) {
+        int nRows = board.length + 6;
+        int nCols = board[0].length() + 6;
+
+        grid = new int[nRows][nCols];
+
+        for (int r = 0; r < nRows; r++) {
+            Arrays.fill(grid[r], -1);
+            for (int c = 3; c < nCols - 3; c++)
+                if (r >= 3 && r < nRows - 3) {
+                    if (board[r - 3].charAt(c - 3) == '0') {
+                        grid[r][c] = 0;
+                        totalToFill++;
+                    }
+                }
+        }
+
+        int pos = -1, r, c;
+        do {
+            do {
+                pos++;
+                r = pos / nCols;
+                c = pos % nCols;
+            } while (grid[r][c] == -1);
+
+            grid[r][c] = 1;
+            if (solve(r, c, 2))
+                break;
+            grid[r][c] = 0;
+
+        } while (pos < nRows * nCols);
+
+        printResult();
+    }
+
+    static boolean solve(int r, int c, int count) {
+        if (count > totalToFill)
+            return true;
+
+        List<int[]> nbrs = neighbors(r, c);
+
+        if (nbrs.isEmpty() && count != totalToFill)
+            return false;
+
+        Collections.sort(nbrs, (a, b) -> a[2] - b[2]);
+
+        for (int[] nb : nbrs) {
+            r = nb[0];
+            c = nb[1];
+            grid[r][c] = count;
+            if (solve(r, c, count + 1))
+                return true;
+            grid[r][c] = 0;
+        }
+
+        return false;
+    }
+
+    static List<int[]> neighbors(int r, int c) {
+        List<int[]> nbrs = new ArrayList<>();
+
+        for (int[] m : moves) {
+            int x = m[0];
+            int y = m[1];
+            if (grid[r + y][c + x] == 0) {
+                int num = countNeighbors(r + y, c + x) - 1;
+                nbrs.add(new int[]{r + y, c + x, num});
+            }
+        }
+        return nbrs;
+    }
+
+    static int countNeighbors(int r, int c) {
+        int num = 0;
+        for (int[] m : moves)
+            if (grid[r + m[1]][c + m[0]] == 0)
+                num++;
+        return num;
+    }
+
+    static void printResult() {
+        for (int[] row : grid) {
+            for (int i : row) {
+                if (i == -1)
+                    System.out.printf("%2s ", ' ');
+                else
+                    System.out.printf("%2d ", i);
+            }
+            System.out.println();
+        }
+    }
+}