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dwite201012p4.java
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dwite201012p4.java
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/*
* DWITE programming contest solutions
* December 2010 - Problem 4: "Forest Fires"
* Copyright (c) Project Nayuki. All rights reserved.
*
* https://www.nayuki.io/page/dwite-programming-contest-solutions
* https://github.com/nayuki/DWITE-programming-contest-solutions
*/
public final class dwite201012p4 extends DwiteSolution {
public static void main(String[] args) {
new dwite201012p4().run("DATA4.txt", "OUT4.txt");
}
protected void runOnce() {
final int WIDTH = 10;
final int HEIGHT = 10;
// Read map and pad
char[][] map = DwiteAlgorithm.newCharGrid(HEIGHT + 2, WIDTH + 2, '.');
for (int i = 0; i < HEIGHT; i++) {
String line = io.readLine();
for (int j = 0; j < WIDTH; j++)
map[i + 1][j + 1] = line.charAt(j);
}
io.readLine(); // Discard line of hyphens
// Initialize distances
int[][] distance = new int[HEIGHT + 2][WIDTH + 2];
for (int i = 0; i < HEIGHT + 2; i++) {
for (int j = 0; j < WIDTH + 2; j++) {
distance[i][j] = switch (map[i][j]) {
case '.' -> 999;
case 'T' -> 999;
case 'F' -> 0;
default -> throw new IllegalArgumentException();
};
}
}
// Compute all minimum distances (Bellman-Ford)
for (int i = 0; i < WIDTH * HEIGHT; i++) {
for (int j = 0; j < HEIGHT; j++) {
for (int k = 0; k < WIDTH; k++) {
if (map[j + 1][k + 1] == 'T') {
int d = distance[j + 1][k + 1];
d = Math.min(distance[j + 1][k + 0] + 1, d);
d = Math.min(distance[j + 1][k + 2] + 1, d);
d = Math.min(distance[j + 0][k + 1] + 1, d);
d = Math.min(distance[j + 2][k + 1] + 1, d);
distance[j + 1][k + 1] = d;
}
}
}
}
// Find maximum distance
int max = 0;
for (int i = 0; i < HEIGHT; i++) {
for (int j = 0; j < WIDTH; j++) {
if (map[i + 1][j + 1] == 'T')
max = Math.max(distance[i + 1][j + 1], max);
}
}
if (max != 999)
io.println(max);
else
io.println(-1);
}
}