418 lines
9.6 KiB
Java
418 lines
9.6 KiB
Java
/*
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* Pixel Dungeon
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* Copyright (C) 2012-2015 Oleg Dolya
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*
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* Shattered Pixel Dungeon
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* Copyright (C) 2014-2025 Evan Debenham
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*
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* This program is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>
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*/
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package com.watabou.utils;
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import java.util.Arrays;
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import java.util.LinkedList;
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public class PathFinder {
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public static int[] distance;
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private static int[] maxVal;
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private static boolean[] goals;
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private static int[] queue;
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private static boolean[] queued; //currently only used in getStepBack, other can piggyback on distance
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private static int size = 0;
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private static int width = 0;
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private static int[] dir;
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private static int[] dirLR;
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//performance-light shortcuts for some common pathfinder cases
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//they are in array-access order for increased memory performance
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public static int[] NEIGHBOURS4;
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public static int[] NEIGHBOURS8;
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public static int[] NEIGHBOURS9;
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//similar to their equivalent neighbour arrays, but the order is clockwise.
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//Useful for some logic functions, but is slower due to lack of array-access order.
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public static int[] CIRCLE4;
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public static int[] CIRCLE8;
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public static void setMapSize( int width, int height ) {
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PathFinder.width = width;
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PathFinder.size = width * height;
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distance = new int[size];
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goals = new boolean[size];
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queue = new int[size];
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queued = new boolean[size];
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maxVal = new int[size];
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Arrays.fill(maxVal, Integer.MAX_VALUE);
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dir = new int[]{-1, +1, -width, +width, -width-1, -width+1, +width-1, +width+1};
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dirLR = new int[]{-1-width, -1, -1+width, -width, +width, +1-width, +1, +1+width};
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NEIGHBOURS4 = new int[]{-width, -1, +1, +width};
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NEIGHBOURS8 = new int[]{-width-1, -width, -width+1, -1, +1, +width-1, +width, +width+1};
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NEIGHBOURS9 = new int[]{-width-1, -width, -width+1, -1, 0, +1, +width-1, +width, +width+1};
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CIRCLE4 = new int[]{-width, +1, +width, -1};
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CIRCLE8 = new int[]{-width-1, -width, -width+1, +1, +width+1, +width, +width-1, -1};
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}
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public static Path find( int from, int to, boolean[] passable ) {
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if (!buildDistanceMap( from, to, passable )) {
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return null;
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}
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Path result = new Path();
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int s = from;
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// From the starting position we are moving downwards,
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// until we reach the ending point
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do {
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int minD = distance[s];
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int mins = s;
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for (int i=0; i < dir.length; i++) {
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int n = s + dir[i];
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int thisD = distance[n];
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if (thisD < minD) {
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minD = thisD;
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mins = n;
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}
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}
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s = mins;
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result.add( s );
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} while (s != to);
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return result;
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}
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public static int getStep( int from, int to, boolean[] passable ) {
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if (!buildDistanceMap( from, to, passable )) {
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return -1;
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}
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// From the starting position we are making one step downwards
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int minD = distance[from];
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int best = from;
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int step, stepD;
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for (int i=0; i < dir.length; i++) {
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if ((stepD = distance[step = from + dir[i]]) < minD) {
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minD = stepD;
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best = step;
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}
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}
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return best;
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}
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public static int getStepBack( int cur, int from, int lookahead, boolean[] passable, boolean canApproachFromPos ) {
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int d = buildEscapeDistanceMap( cur, from, lookahead, passable );
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if (d == 0) return -1;
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if (!canApproachFromPos) {
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//We can't approach the position we are retreating from
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//re-calculate based on this, and reduce the target distance if need-be
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int head = 0;
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int tail = 0;
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int newD = distance[cur];
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BArray.setFalse(queued);
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queue[tail++] = cur;
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queued[cur] = true;
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while (head < tail) {
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int step = queue[head++];
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if (distance[step] > newD) {
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newD = distance[step];
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}
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int start = (step % width == 0 ? 3 : 0);
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int end = ((step + 1) % width == 0 ? 3 : 0);
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for (int i = start; i < dirLR.length - end; i++) {
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int n = step + dirLR[i];
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if (n >= 0 && n < size && passable[n]) {
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if (distance[n] < distance[cur]) {
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passable[n] = false;
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} else if (distance[n] >= distance[step] && !queued[n]) {
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// Add to queue
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queue[tail++] = n;
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queued[n] = true;
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}
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}
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}
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}
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d = Math.min(newD, d);
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}
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for (int i=0; i < size; i++) {
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goals[i] = distance[i] == d;
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}
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if (!buildDistanceMap( cur, goals, passable )) {
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return -1;
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}
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int s = cur;
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// From the starting position we are making one step downwards
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int minD = distance[s];
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int mins = s;
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for (int i=0; i < dir.length; i++) {
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int n = s + dir[i];
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int thisD = distance[n];
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if (thisD < minD) {
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minD = thisD;
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mins = n;
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}
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}
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return mins;
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}
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private static boolean buildDistanceMap( int from, int to, boolean[] passable ) {
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if (from == to) {
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return false;
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}
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System.arraycopy(maxVal, 0, distance, 0, maxVal.length);
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boolean pathFound = false;
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int head = 0;
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int tail = 0;
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// Add to queue
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queue[tail++] = to;
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distance[to] = 0;
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while (head < tail) {
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// Remove from queue
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int step = queue[head++];
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if (step == from) {
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pathFound = true;
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break;
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}
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int nextDistance = distance[step] + 1;
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int start = (step % width == 0 ? 3 : 0);
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int end = ((step+1) % width == 0 ? 3 : 0);
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for (int i = start; i < dirLR.length - end; i++) {
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int n = step + dirLR[i];
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if (n == from || (n >= 0 && n < size && passable[n] && (distance[n] > nextDistance))) {
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// Add to queue
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queue[tail++] = n;
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distance[n] = nextDistance;
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}
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}
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}
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return pathFound;
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}
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public static void buildDistanceMap( int to, boolean[] passable, int limit ) {
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System.arraycopy(maxVal, 0, distance, 0, maxVal.length);
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int head = 0;
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int tail = 0;
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// Add to queue
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queue[tail++] = to;
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distance[to] = 0;
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while (head < tail) {
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// Remove from queue
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int step = queue[head++];
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int nextDistance = distance[step] + 1;
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if (nextDistance > limit) {
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return;
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}
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int start = (step % width == 0 ? 3 : 0);
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int end = ((step+1) % width == 0 ? 3 : 0);
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for (int i = start; i < dirLR.length - end; i++) {
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int n = step + dirLR[i];
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if (n >= 0 && n < size && passable[n] && (distance[n] > nextDistance)) {
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// Add to queue
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queue[tail++] = n;
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distance[n] = nextDistance;
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}
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}
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}
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}
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private static boolean buildDistanceMap( int from, boolean[] to, boolean[] passable ) {
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if (to[from]) {
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return false;
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}
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System.arraycopy(maxVal, 0, distance, 0, maxVal.length);
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boolean pathFound = false;
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int head = 0;
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int tail = 0;
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// Add to queue
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for (int i=0; i < size; i++) {
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if (to[i]) {
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queue[tail++] = i;
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distance[i] = 0;
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}
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}
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while (head < tail) {
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// Remove from queue
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int step = queue[head++];
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if (step == from) {
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pathFound = true;
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break;
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}
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int nextDistance = distance[step] + 1;
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int start = (step % width == 0 ? 3 : 0);
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int end = ((step+1) % width == 0 ? 3 : 0);
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for (int i = start; i < dirLR.length - end; i++) {
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int n = step + dirLR[i];
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if (n == from || (n >= 0 && n < size && passable[n] && (distance[n] > nextDistance))) {
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// Add to queue
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queue[tail++] = n;
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distance[n] = nextDistance;
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}
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}
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}
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return pathFound;
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}
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//the lookahead is the target number of cells to retreat toward from our current position's
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// distance from the position we are escaping from. Returns the highest found distance, up to the lookahead
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private static int buildEscapeDistanceMap( int cur, int from, int lookAhead, boolean[] passable ) {
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System.arraycopy(maxVal, 0, distance, 0, maxVal.length);
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int destDist = Integer.MAX_VALUE;
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int head = 0;
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int tail = 0;
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// Add to queue
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queue[tail++] = from;
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distance[from] = 0;
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int dist = 0;
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while (head < tail) {
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// Remove from queue
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int step = queue[head++];
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dist = distance[step];
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if (dist > destDist) {
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return destDist;
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}
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if (step == cur) {
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destDist = dist + lookAhead;
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}
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int nextDistance = dist + 1;
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int start = (step % width == 0 ? 3 : 0);
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int end = ((step+1) % width == 0 ? 3 : 0);
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for (int i = start; i < dirLR.length - end; i++) {
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int n = step + dirLR[i];
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if (n >= 0 && n < size && passable[n] && distance[n] > nextDistance) {
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// Add to queue
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queue[tail++] = n;
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distance[n] = nextDistance;
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}
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}
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}
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return dist;
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}
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public static void buildDistanceMap( int to, boolean[] passable ) {
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System.arraycopy(maxVal, 0, distance, 0, maxVal.length);
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int head = 0;
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int tail = 0;
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// Add to queue
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queue[tail++] = to;
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distance[to] = 0;
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while (head < tail) {
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// Remove from queue
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int step = queue[head++];
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int nextDistance = distance[step] + 1;
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int start = (step % width == 0 ? 3 : 0);
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int end = ((step+1) % width == 0 ? 3 : 0);
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for (int i = start; i < dirLR.length - end; i++) {
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int n = step + dirLR[i];
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if (n >= 0 && n < size && passable[n] && (distance[n] > nextDistance)) {
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// Add to queue
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queue[tail++] = n;
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distance[n] = nextDistance;
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}
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}
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}
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}
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@SuppressWarnings("serial")
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public static class Path extends LinkedList<Integer> {
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}
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}
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