001 package aima.search.nqueens;
002
003 import java.util.ArrayList;
004 import java.util.List;
005
006 import aima.basic.XYLocation;
007
008 public class NQueensBoard {
009
010 /**
011 * X---> increases left to right with zero based index Y increases top to
012 * bottom with zero based index | | V
013 */
014 int[][] board;
015
016 int size;
017
018 public NQueensBoard(int n) {
019
020 size = n;
021 board = new int[size][size];
022 for (int i = 0; i < size; i++) {
023 for (int j = 0; j < size; j++) {
024 board[i][j] = 0;
025 }
026 }
027 }
028
029 public void addQueenAt(XYLocation l) {
030
031 if (!(queenExistsAt(l)))
032 board[l.getXCoOrdinate()][l.getYCoOrdinate()] = 1;
033 }
034
035 public void removeQueenFrom(XYLocation l) {
036
037 if (board[l.getXCoOrdinate()][l.getYCoOrdinate()] == 1) {
038 board[l.getXCoOrdinate()][l.getYCoOrdinate()] = 0;
039 }
040 }
041
042 private boolean queenExistsAt(int x, int y) {
043
044 return (board[x][y] == 1);
045 }
046
047 public boolean queenExistsAt(XYLocation l) {
048
049 return (queenExistsAt(l.getXCoOrdinate(), l.getYCoOrdinate()));
050 }
051
052 public void moveQueen(XYLocation from, XYLocation to) {
053
054 if ((queenExistsAt(from)) && (!(queenExistsAt(to)))) {
055 removeQueenFrom(from);
056 addQueenAt(to);
057 }
058 }
059
060 public void clear() {
061
062 for (int i = 0; i < size; i++) {
063 for (int j = 0; j < size; j++) {
064 board[i][j] = 0;
065 }
066 }
067 }
068
069 public void setBoard(List<XYLocation> al) {
070
071 clear();
072
073 for (int i = 0; i < al.size(); i++) {
074 addQueenAt(al.get(i));
075 }
076 }
077
078 public int getNumberOfQueensOnBoard() {
079
080 int count = 0;
081 for (int i = 0; i < size; i++) {
082 for (int j = 0; j < size; j++) {
083 if (board[i][j] == 1) {
084 count++;
085 }
086 }
087 }
088 return count;
089 }
090
091 public List<XYLocation> getQueenPositions() {
092
093 ArrayList<XYLocation> result = new ArrayList<XYLocation>();
094 for (int i = 0; i < size; i++) {
095 for (int j = 0; j < size; j++) {
096 if (queenExistsAt(i, j)) {
097 result.add(new XYLocation(i, j));
098 }
099 }
100 }
101 return result;
102
103 }
104
105 private boolean isSquareHorizontallyAttacked(int x, int y) {
106
107 return numberOfHorizontalAttacksOn(x, y) > 0;
108 }
109
110 private boolean isSquareVerticallyAttacked(int x, int y) {
111 return numberOfVerticalAttacksOn(x, y) > 0;
112 }
113
114 private boolean isSquareDiagonallyAttacked(int x, int y) {
115 return numberOfDiagonalAttacksOn(x, y) > 0;
116 }
117
118 public boolean isSquareUnderAttack(XYLocation l) {
119
120 int x = l.getXCoOrdinate();
121 int y = l.getYCoOrdinate();
122 return (isSquareHorizontallyAttacked(x, y)
123 || isSquareVerticallyAttacked(x, y) || isSquareDiagonallyAttacked(
124 x, y));
125 }
126
127 public int getSize() {
128
129 return size;
130 }
131
132 public void print() {
133
134 System.out.println(getBoardPic());
135
136 }
137
138 public String getBoardPic() {
139
140 StringBuffer buffer = new StringBuffer();
141 for (int row = 0; (row < size); row++) { // row
142 for (int col = 0; (col < size); col++) { // col
143 if (queenExistsAt(col, row)) {
144 buffer.append(" Q ");
145 } else {
146 buffer.append(" - ");
147 }
148 }
149 buffer.append("\n");
150 }
151 return buffer.toString();
152 }
153
154 public int getNumberOfAttacksOn(XYLocation l) {
155
156 int x = l.getXCoOrdinate();
157 int y = l.getYCoOrdinate();
158 return numberOfHorizontalAttacksOn(x, y)
159 + numberOfVerticalAttacksOn(x, y)
160 + numberOfDiagonalAttacksOn(x, y);
161 }
162
163 private int numberOfHorizontalAttacksOn(int x, int y) {
164
165 int retVal = 0;
166 for (int i = 0; i < size; i++) {
167 if ((queenExistsAt(i, y))) {
168 if (i != x)
169 retVal++;
170 }
171 }
172 return retVal;
173 }
174
175 private int numberOfVerticalAttacksOn(int x, int y) {
176
177 int retVal = 0;
178 for (int j = 0; j < size; j++) {
179 if ((queenExistsAt(x, j))) {
180 if (j != y)
181 retVal++;
182 }
183 }
184 return retVal;
185 }
186
187 private int numberOfDiagonalAttacksOn(int x, int y) {
188
189 int retVal = 0;
190
191 int i;
192 int j;
193 // forward up diagonal
194 for (i = (x + 1), j = (y - 1); (i < size && (j > -1)); i++, j--) {
195 if (queenExistsAt(i, j)) {
196 retVal++;
197 }
198 }
199 // forward down diagonal
200 for (i = (x + 1), j = (y + 1); ((i < size) && (j < size)); i++, j++) {
201 if (queenExistsAt(i, j)) {
202 retVal++;
203 }
204 }
205 // backward up diagonal
206 for (i = (x - 1), j = (y - 1); ((i > -1) && (j > -1)); i--, j--) {
207 if (queenExistsAt(i, j)) {
208 retVal++;
209 }
210 }
211
212 // backward down diagonal
213 for (i = (x - 1), j = (y + 1); ((i > -1) && (j < size)); i--, j++) {
214 if (queenExistsAt(i, j)) {
215 retVal++;
216 }
217 }
218
219 return retVal;
220 }
221
222 @Override
223 public int hashCode() {
224 List<XYLocation> locs = getQueenPositions();
225
226 int result = 17;
227 for (XYLocation loc : locs) {
228 result = 37 * loc.hashCode();
229 }
230 return result;
231 }
232
233 @Override
234 public boolean equals(Object o) {
235
236 if (this == o) {
237 return true;
238 }
239 if ((o == null) || (this.getClass() != o.getClass())) {
240 return false;
241 }
242 NQueensBoard aBoard = (NQueensBoard) o;
243 boolean retVal = true;
244 List<XYLocation> locs = getQueenPositions();
245
246 for (XYLocation loc : locs) {
247 if (!(aBoard.queenExistsAt(loc))) {
248 retVal = false;
249 }
250 }
251 return retVal;
252 }
253
254 @Override
255 public String toString() {
256 StringBuffer buf = new StringBuffer();
257 for (int row = 0; row < size; row++) { // rows
258 for (int col = 0; col < size; col++) { // columns
259 if (queenExistsAt(col, row)) {
260 buf.append('Q');
261 } else {
262 buf.append('-');
263 }
264 }
265 buf.append("\n");
266 }
267 return buf.toString();
268 }
269
270 }