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/* vim: set expandtab tabstop=4 shiftwidth=4 : */
class Board {
private int d;
private byte[][] blocks;
private int openRow;
private int openCol;
private Board(byte[][] blocks, int openI, int openJ)
{
this.d = blocks[0].length;
this.blocks = blocks;
this.openRow = openI;
this.openCol = openJ;
}
// construct a board from an N-by-N array of blocks
// (where blocks[i][j] = block in row i, column j)
public Board(int[][] blocks)
{
this.d = blocks[0].length;
this.openRow = this.d - 1;
this.openCol = this.d - 1;
this.blocks = new byte[d][d];
for (int i = 0; i < d; i++)
for (int j = 0; j < d; j++)
this.blocks[i][j] = (byte) blocks[i][j];
}
// board dimension N
public int dimension()
{
return d;
}
// number of blocks out of place
public int hamming()
{
int k = 1;
int hamming = 0;
for (int i = 0; i < d; i++)
for (int j = 0; j < d; j++, k++)
if (blocks[i][j] != 0 && blocks[i][j] != k) hamming += 1;
return hamming;
}
// sum of Manhattan distances between blocks and goal
public int manhattan()
{
int manhattan = 0;
for (int i = 0; i < d; i++)
for (int j = 0; j < d; j++)
{
int v = blocks[i][j] -1;
if (v == -1) continue;
manhattan += Math.abs((v / d) - i) + Math.abs((v % d) - j);
}
return manhattan;
}
// is this board the goal board?
public boolean isGoal()
{
int k = 1;
if (blocks[d-1][d-1] != 0) return false;
for (int i = 0; i < d; i++)
for (int j = 0; j < d; j++)
if (blocks[i][j] != k++ && !((i == j) && (j == d - 1))) return false;
return true;
}
private Board swap(int r0, int c0, int r1, int c1)
{
byte[][] blocks2 = new byte[d][d];
for (int i = 0; i < d; i++)
for (int j = 0; j < d; j++)
blocks2[i][j] = blocks[i][j];
byte tmp = blocks2[r0][c0];
blocks2[r0][c0] = blocks2[r1][c1];
blocks2[r1][c1] = tmp;
return new Board(blocks2, openRow, openCol);
}
// a board obtained by exchanging two adjacent blocks in the same row
public Board twin()
{
int row = 0;
if (openRow == 0) row = 1;
return swap(row, 0, row, 1);
}
// does this board equal y?
public boolean equals(Object y)
{
if (y == null) return false;
if (y.getClass() != this.getClass()) return false;
Board other = (Board) y;
if (d != other.dimension()) return false;
for (int i = 0; i < d; i++)
for (int j = 0; j < d; j++)
if (blocks[i][j] == other.blocks[i][j]) return true;
return false;
}
// all neighboring boards
public Iterable<Board> neighbors()
{
Queue<Board> q = new Queue<Board>();
if (openRow != 0)
q.enqueue(swap(openRow, openCol, openRow - 1, openCol));
if (openRow < d - 1)
q.enqueue(swap(openRow, openCol, openRow + 1, openCol));
if (openCol != 0)
q.enqueue(swap(openRow, openCol, openRow, openCol - 1));
if (openCol < d - 1)
q.enqueue(swap(openRow, openCol, openRow, openCol + 1));
return q;
}
// string representation of the board
public String toString()
{
String out = "";
for (int i = 0; i < d; i++)
{
for (int j = 0; j < d; j++)
out += " "+(int) blocks[i][j];
out += "\n";
}
// out += "goal "+(isGoal() ? "OK" : "KO")+"\n";
// out += "hamming "+hamming()+"\n";
// out += "manhattan "+manhattan()+"\n";
return out;
}
}
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