public class FifteenPuzzle {
//---------------------------------------------------
public static boolean solvable15Puzzle(int[][] b) {
int a[] = new int[b.length * b[0].length-1];
int run = 0, zero = 0;
for (int i = 0; i < b.length; i++) {
for (int j = 0; j < b[i].length; j++) {
if (b[i][j] != 0) {
a[run] = b[i][j];
run++;
} else {
zero = i+1;
}
}
}
int count = 0;
for (int i = 0; i < a.length; i++) {
for (int j = i + 1; j < a.length; j++) {
if (a[i] > a[j]) count++;
}
}
if ((count + zero) % 2 == 0) return true;
else return false;
}
//---------------------------------------------------
public static void main(String[] a) {
int[][] ok = { { 1, 2, 3, 4 },
{ 5, 6, 7, 8 },
{ 9, 10, 12, 15 },
{ 13, 14, 11, 0 } };
int[][] nok = { { 1, 2, 3, 4 },
{ 5, 6, 7, 8 },
{ 9, 10, 11, 12 },
{ 13, 15, 14, 0 } };
System.out.println(solvable15Puzzle(ok));
System.out.println(solvable15Puzzle(nok));
}
}
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