Pentomino tiling
Pentomino tiling is a draft programming task. It is not yet considered ready to be promoted as a complete task, for reasons that should be found in its talk page.
A pentomino is a polyomino that consists of 5 squares. There are 12 pentomino shapes, if you don't count rotations and reflections. Most pentominoes can form their own mirror image through rotation, but some of them have to be flipped over.
I
I L N Y
FF I L NN PP TTT V W X YY ZZ
FF I L N PP T U U V WW XXX Y Z
F I LL N P T UUU VVV WW X Y ZZ
A Pentomino tiling is an example of an exact cover problem and can take on many forms.
A traditional tiling forms an 8 by 8 grid, where 4 cells are left uncovered. The other cells are covered
by the 12 pentomino shapes, without overlaps, with every shape only used once.
The 4 uncovered cells should be chosen at random. Note that not all configurations are solvable.
The task: create an 8 by 8 tiling and print the result.
For instance:
F I I I I I L N F F F L L L L N W F - X Z Z N N W W X X X Z N V T W W X - Z Z V T T T P P V V V T Y - P P U U U Y Y Y Y P U - U
- Cf.
Java
<lang java>import java.util.*;
public class PentominoTiling {
static final char[] symbols = "FILNPTUVWXYZ-".toCharArray(); static final Random rand = new Random();
static final int nRows = 8; static final int nCols = 8; static final int target = 12; static final int blank = 12;
static int[][] grid = new int[nRows][nCols]; static boolean[] placed = new boolean[target];
public static void main(String[] args) {
for (int r = 0; r < nRows; r++)
Arrays.fill(grid[r], -1);
for (int i = 0; i < 4; i++)
grid[rand.nextInt(nRows)][rand.nextInt(nCols)] = blank;
if (solve(0, 0)) {
printResult();
} else {
System.out.println("no solution");
}
}
static void printResult() {
for (int[] r : grid) {
for (int i : r)
System.out.printf("%c ", symbols[i]);
System.out.println();
}
}
static boolean tryPlaceOrientation(int[] o, int r, int c, int shapeIdx) {
for (int i = 0; i < o.length; i += 2) {
if (r + o[i] < 0 || r + o[i] >= nRows || c + o[i + 1] < 0
|| c + o[i + 1] >= nCols
|| grid[r + o[i]][c + o[i + 1]] != -1)
return false;
}
grid[r][c] = shapeIdx;
for (int i = 0; i < o.length; i += 2)
grid[r + o[i]][c + o[i + 1]] = shapeIdx;
return true; }
static void removeOrientation(int[] o, int r, int c) {
grid[r][c] = -1;
for (int i = 0; i < o.length; i += 2)
grid[r + o[i]][c + o[i + 1]] = -1;
}
static boolean solve(int pos, int numPlaced) {
if (numPlaced == target)
return true;
int row = pos / nCols;
int col = pos % nCols;
if (grid[row][col] != -1)
return solve(pos + 1, numPlaced);
for (int i = 0; i < shapes.length; i++) {
if (!placed[i]) {
for (int[] orientation : shapes[i]) {
if (!tryPlaceOrientation(orientation, row, col, i))
continue;
placed[i] = true;
if (solve(pos + 1, numPlaced + 1))
return true;
removeOrientation(orientation, row, col);
placed[i] = false;
}
}
}
return false;
}
static final int[][] F = {{1, -1, 1, 0, 1, 1, 2, 1}, {0, 1, 1, -1, 1, 0, 2, 0},
{1, 0, 1, 1, 1, 2, 2, 1}, {1, 0, 1, 1, 2, -1, 2, 0}, {1, -2, 1, -1, 1, 0, 2, -1},
{0, 1, 1, 1, 1, 2, 2, 1}, {1, -1, 1, 0, 1, 1, 2, -1}, {1, -1, 1, 0, 2, 0, 2, 1}};
static final int[][] I = {{0, 1, 0, 2, 0, 3, 0, 4}, {1, 0, 2, 0, 3, 0, 4, 0}};
static final int[][] L = {{1, 0, 1, 1, 1, 2, 1, 3}, {1, 0, 2, 0, 3, -1, 3, 0},
{0, 1, 0, 2, 0, 3, 1, 3}, {0, 1, 1, 0, 2, 0, 3, 0}, {0, 1, 1, 1, 2, 1, 3, 1},
{0, 1, 0, 2, 0, 3, 1, 0}, {1, 0, 2, 0, 3, 0, 3, 1}, {1, -3, 1, -2, 1, -1, 1, 0}};
static final int[][] N = {{0, 1, 1, -2, 1, -1, 1, 0}, {1, 0, 1, 1, 2, 1, 3, 1},
{0, 1, 0, 2, 1, -1, 1, 0}, {1, 0, 2, 0, 2, 1, 3, 1}, {0, 1, 1, 1, 1, 2, 1, 3},
{1, 0, 2, -1, 2, 0, 3, -1}, {0, 1, 0, 2, 1, 2, 1, 3}, {1, -1, 1, 0, 2, -1, 3, -1}};
static final int[][] P = {{0, 1, 1, 0, 1, 1, 2, 1}, {0, 1, 0, 2, 1, 0, 1, 1},
{1, 0, 1, 1, 2, 0, 2, 1}, {0, 1, 1, -1, 1, 0, 1, 1}, {0, 1, 1, 0, 1, 1, 1, 2},
{1, -1, 1, 0, 2, -1, 2, 0}, {0, 1, 0, 2, 1, 1, 1, 2}, {0, 1, 1, 0, 1, 1, 2, 0}};
static final int[][] T = {{0, 1, 0, 2, 1, 1, 2, 1}, {1, -2, 1, -1, 1, 0, 2, 0},
{1, 0, 2, -1, 2, 0, 2, 1}, {1, 0, 1, 1, 1, 2, 2, 0}};
static final int[][] U = {{0, 1, 0, 2, 1, 0, 1, 2}, {0, 1, 1, 1, 2, 0, 2, 1},
{0, 2, 1, 0, 1, 1, 1, 2}, {0, 1, 1, 0, 2, 0, 2, 1}};
static final int[][] V = {{1, 0, 2, 0, 2, 1, 2, 2}, {0, 1, 0, 2, 1, 0, 2, 0},
{1, 0, 2, -2, 2, -1, 2, 0}, {0, 1, 0, 2, 1, 2, 2, 2}};
static final int[][] W = {{1, 0, 1, 1, 2, 1, 2, 2}, {1, -1, 1, 0, 2, -2, 2, -1},
{0, 1, 1, 1, 1, 2, 2, 2}, {0, 1, 1, -1, 1, 0, 2, -1}};
static final int[][] X = Template:1, -1, 1, 0, 1, 1, 2, 0;
static final int[][] Y = {{1, -2, 1, -1, 1, 0, 1, 1}, {1, -1, 1, 0, 2, 0, 3, 0},
{0, 1, 0, 2, 0, 3, 1, 1}, {1, 0, 2, 0, 2, 1, 3, 0}, {0, 1, 0, 2, 0, 3, 1, 2},
{1, 0, 1, 1, 2, 0, 3, 0}, {1, -1, 1, 0, 1, 1, 1, 2}, {1, 0, 2, -1, 2, 0, 3, 0}};
static final int[][] Z = {{0, 1, 1, 0, 2, -1, 2, 0}, {1, 0, 1, 1, 1, 2, 2, 2},
{0, 1, 1, 1, 2, 1, 2, 2}, {1, -2, 1, -1, 1, 0, 2, -2}};
static final int[][][] shapes = {F, I, L, N, P, T, U, V, W, X, Y, Z};
}</lang>
F I I I I I L L F F F P P V L - Z F P P P V L N Z Z Z V V V L N - X Z - W W N N X X X W W - N T U X U W Y T T T U U U Y Y Y Y T