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Board.java
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158 lines (122 loc) · 4.66 KB
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/**
* Created by merlin on 17/2/19.
*/
import java.util.LinkedList;
public class Board {
private static final int SPACE = 0;
private int[][] blocks;
public Board(int[][] blocks) {
this.blocks = copy(blocks);
}
private int[][] copy(int[][] blocks) {
int[][] copy = new int[blocks.length][blocks.length];
for (int row = 0; row < blocks.length; row++)
for (int col = 0; col < blocks.length; col++)
copy[row][col] = blocks[row][col];
return copy;
}
public int dimension() {
return blocks.length;
}
public int hamming() {
int count = 0;
for (int row = 0; row < blocks.length; row++)
for (int col = 0; col < blocks.length; col++)
if (blockIsNotInPlace(row, col)) count++;
return count;
}
private boolean blockIsNotInPlace(int row, int col) {
int block = block(row, col);
return !isSpace(block) && block != goalFor(row, col);
}
private int goalFor(int row, int col) {
return row*dimension() + col + 1;
}
private boolean isSpace(int block) {
return block == SPACE;
}
public int manhattan() {
int sum = 0;
for (int row = 0; row < blocks.length; row++)
for (int col = 0; col < blocks.length; col++)
sum += calculateDistances(row, col);
return sum;
}
private int calculateDistances(int row, int col) {
int block = block(row, col);
return (isSpace(block)) ? 0 : Math.abs(row - row(block)) + Math.abs(col - col(block));
}
private int block(int row, int col) {
return blocks[row][col];
}
private int row (int block) {
return (block - 1) / dimension();
}
private int col (int block) {
return (block - 1) % dimension();
}
public boolean isGoal() {
for (int row = 0; row < blocks.length; row++)
for (int col = 0; col < blocks.length; col++)
if (blockIsInPlace(row, col)) return false;
return true;
}
private boolean blockIsInPlace(int row, int col) {
int block = block(row, col);
return !isSpace(block) && block != goalFor(row, col);
}
public Board twin() {
for (int row = 0; row < blocks.length; row++)
for (int col = 0; col < blocks.length - 1; col++)
if (!isSpace(block(row, col)) && !isSpace(block(row, col + 1)))
return new Board(swap(row, col, row, col + 1));
throw new RuntimeException();
}
private int[][] swap(int row1, int col1, int row2, int col2) {
int[][] copy = copy(blocks);
int tmp = copy[row1][col1];
copy[row1][col1] = copy[row2][col2];
copy[row2][col2] = tmp;
return copy;
}
public boolean equals(Object y) {
if (y==this) return true;
if (y==null || !(y instanceof Board) || ((Board)y).blocks.length != blocks.length) return false;
for (int row = 0; row < blocks.length; row++)
for (int col = 0; col < blocks.length; col++)
if (((Board) y).blocks[row][col] != block(row, col)) return false;
return true;
}
public Iterable<Board> neighbors() {
LinkedList<Board> neighbors = new LinkedList<Board>();
int[] location = spaceLocation();
int spaceRow = location[0];
int spaceCol = location[1];
if (spaceRow > 0) neighbors.add(new Board(swap(spaceRow, spaceCol, spaceRow - 1, spaceCol)));
if (spaceRow < dimension() - 1) neighbors.add(new Board(swap(spaceRow, spaceCol, spaceRow + 1, spaceCol)));
if (spaceCol > 0) neighbors.add(new Board(swap(spaceRow, spaceCol, spaceRow, spaceCol - 1)));
if (spaceCol < dimension() - 1) neighbors.add(new Board(swap(spaceRow, spaceCol, spaceRow, spaceCol + 1)));
return neighbors;
}
private int[] spaceLocation() {
for (int row = 0; row < blocks.length; row++)
for (int col = 0; col < blocks.length; col++)
if (isSpace(block(row, col))) {
int[] location = new int[2];
location[0] = row;
location[1] = col;
return location;
}
throw new RuntimeException();
}
public String toString() {
StringBuilder str = new StringBuilder();
str.append(dimension() + "\n");
for (int row = 0; row < blocks.length; row++) {
for (int col = 0; col < blocks.length; col++)
str.append(String.format("%2d ", block(row, col)));
str.append("\n");
}
return str.toString();
}
}