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