Data commit

Task/Sokoban/Java/sokoban.java

@@ -0,0 +1,138 @@
+import java.util.*;
+
+public class Sokoban {
+    String destBoard, currBoard;
+    int playerX, playerY, nCols;
+
+    Sokoban(String[] board) {
+        nCols = board[0].length();
+        StringBuilder destBuf = new StringBuilder();
+        StringBuilder currBuf = new StringBuilder();
+
+        for (int r = 0; r < board.length; r++) {
+            for (int c = 0; c < nCols; c++) {
+
+                char ch = board[r].charAt(c);
+
+                destBuf.append(ch != '$' && ch != '@' ? ch : ' ');
+                currBuf.append(ch != '.' ? ch : ' ');
+
+                if (ch == '@') {
+                    this.playerX = c;
+                    this.playerY = r;
+                }
+            }
+        }
+        destBoard = destBuf.toString();
+        currBoard = currBuf.toString();
+    }
+
+    String move(int x, int y, int dx, int dy, String trialBoard) {
+
+        int newPlayerPos = (y + dy) * nCols + x + dx;
+
+        if (trialBoard.charAt(newPlayerPos) != ' ')
+            return null;
+
+        char[] trial = trialBoard.toCharArray();
+        trial[y * nCols + x] = ' ';
+        trial[newPlayerPos] = '@';
+
+        return new String(trial);
+    }
+
+    String push(int x, int y, int dx, int dy, String trialBoard) {
+
+        int newBoxPos = (y + 2 * dy) * nCols + x + 2 * dx;
+
+        if (trialBoard.charAt(newBoxPos) != ' ')
+            return null;
+
+        char[] trial = trialBoard.toCharArray();
+        trial[y * nCols + x] = ' ';
+        trial[(y + dy) * nCols + x + dx] = '@';
+        trial[newBoxPos] = '$';
+
+        return new String(trial);
+    }
+
+    boolean isSolved(String trialBoard) {
+        for (int i = 0; i < trialBoard.length(); i++)
+            if ((destBoard.charAt(i) == '.')
+                    != (trialBoard.charAt(i) == '$'))
+                return false;
+        return true;
+    }
+
+    String solve() {
+        class Board {
+            String cur, sol;
+            int x, y;
+
+            Board(String s1, String s2, int px, int py) {
+                cur = s1;
+                sol = s2;
+                x = px;
+                y = py;
+            }
+        }
+        char[][] dirLabels = {{'u', 'U'}, {'r', 'R'}, {'d', 'D'}, {'l', 'L'}};
+        int[][] dirs = {{0, -1}, {1, 0}, {0, 1}, {-1, 0}};
+
+        Set<String> history = new HashSet<>();
+        LinkedList<Board> open = new LinkedList<>();
+
+        history.add(currBoard);
+        open.add(new Board(currBoard, "", playerX, playerY));
+
+        while (!open.isEmpty()) {
+            Board item = open.poll();
+            String cur = item.cur;
+            String sol = item.sol;
+            int x = item.x;
+            int y = item.y;
+
+            for (int i = 0; i < dirs.length; i++) {
+                String trial = cur;
+                int dx = dirs[i][0];
+                int dy = dirs[i][1];
+
+                // are we standing next to a box ?
+                if (trial.charAt((y + dy) * nCols + x + dx) == '$') {
+
+                    // can we push it ?
+                    if ((trial = push(x, y, dx, dy, trial)) != null) {
+
+                        // or did we already try this one ?
+                        if (!history.contains(trial)) {
+
+                            String newSol = sol + dirLabels[i][1];
+
+                            if (isSolved(trial))
+                                return newSol;
+
+                            open.add(new Board(trial, newSol, x + dx, y + dy));
+                            history.add(trial);
+                        }
+                    }
+
+                // otherwise try changing position
+                } else if ((trial = move(x, y, dx, dy, trial)) != null) {
+
+                    if (!history.contains(trial)) {
+                        String newSol = sol + dirLabels[i][0];
+                        open.add(new Board(trial, newSol, x + dx, y + dy));
+                        history.add(trial);
+                    }
+                }
+            }
+        }
+        return "No solution";
+    }
+
+    public static void main(String[] a) {
+        String level = "#######,#     #,#     #,#. #  #,#. $$ #,"
+                + "#.$$  #,#.#  @#,#######";
+        System.out.println(new Sokoban(level.split(",")).solve());
+    }
+}