-
Notifications
You must be signed in to change notification settings - Fork 0
/
BacktrackingSearch.java
296 lines (267 loc) · 7.82 KB
/
BacktrackingSearch.java
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
// Yujun Jiang
// Sudoku Solver implementing Recursive Backtracking, AC-3, and Forward Checking
import java.util.*;
public class BacktrackingSearch {
public static int moveCount = 0;
public static Board board;
// AC-3 variable domains
public static HashMap<Square, ArrayList<Integer>> domains = new HashMap<Square, ArrayList<Integer>>();
public static HashMap<Square, ArrayList<Integer>> inferences = new HashMap<Square, ArrayList<Integer>>();
public static LinkedList<Arc> arcList = new LinkedList<Arc>();
public static HashMap<Square, ArrayList<Integer>> removed = new HashMap<Square, ArrayList<Integer>>();
public static void main(String[] args){
makeBoard();
System.out.println("Puzzle:");
printBoard();
// Initialize domains
for(Square s : board.getVars()){
domains.put(s, board.varDomain(s.row, s.col));
inferences.put(s, board.varDomain(s.row, s.col));
}
if(!solve()){
System.out.println("There is no solution.");
printBoard();
}else{
System.out.println("Solution:");
printBoard();
}
solve();
System.out.println("Number of Assignments: "+moveCount);
}
public static boolean solve(){
// return RecursiveBackTracking(board.nextEmpty());
// return AC3();
// Forward checking
return forwardChecking(board.nextEmpty(), inferences);
}
public static boolean RecursiveBackTracking(Square empty){
if(board.complete()) return true;
// Change back to full domain
// for(int i : board.varDomain(empty.row, empty.col)){
for(int i : domains.get(empty)){
if(board.meetsConstraints(empty.row, empty.col, i)){
board.set(empty.row, empty.col, i);
moveCount++;
}else{
continue;
}
if(RecursiveBackTracking(board.nextEmpty()))
return true;
else
board.set(empty.row, empty.col, 0);
}
return false;
}
public static void forwardCheck(){
board.clear();
for(Square s : domains.keySet()){
if(domains.get(s).size() == 1){
board.set(s.row, s.col, domains.get(s).get(0));
moveCount++;
}
}
// backtrack(board.nextEmpty());
}
public static boolean forwardChecking(Square empty, HashMap<Square, ArrayList<Integer>> doms){
if(board.complete()) return true;
// for(int i : doms.get(empty)){
for(int i : board.varDomain(empty.row, empty.col)){
if(board.meetsConstraints(empty.row, empty.col, i)){
board.set(empty.row, empty.col, i);
moveCount++;
// remove
// for(Square s : board.getNeighbors(empty.row, empty.col)){
// if(s!=empty) inferences.get(s).remove(new Integer(i));
// }
for(Square s : board.getNeighbors(empty.row, empty.col)){
if(inferences.get(s).size() == 0 && s!=empty){ // If a neighbor has has no values left
doms.get(empty).remove(new Integer(i)); // Remove value from older domains
board.set(empty.row, empty.col, 0); // Remove new assignment
// break;
return forwardChecking(board.nextEmpty(), doms);
}
}
if(forwardChecking(board.nextEmpty(), inferences)){
return true;
}
else{
board.set(empty.row, empty.col, 0);
}
}
}
return false;
}
public static boolean AC3(){
ArrayList<Square> allVars = board.getVars();
// Initialize domains and arcList
for(Square s : allVars)
domains.put(s, board.varDomain(s.row, s.col));
// for(Square s : domains.keySet()) System.out.println(domains.get(s).size());
for(Square s : allVars) {
for(Square t : board.getNeighbors(s.row, s.col)){
Arc newArc = new Arc(s, t);
if(s != t && !arcList.contains(newArc)){
arcList.add(newArc);
}
}
}
Arc arc;
// Outer:
while(arcList.peek() != null){
if(board.complete()) return true;
arc = arcList.poll();
if(domains.get(arc.x).size() > 0 && board.meetsConstraints(arc.x.row, arc.x.col, domains.get(arc.x).get(0))){
if(board.set(arc.x.row, arc.x.col, domains.get(arc.x).get(0)))moveCount++;
}else{
continue;
}
if(revise(arc.x, arc.y)){
if(board.set(arc.x.row, arc.x.col, 0)) moveCount--;
// board.set(arc.y.row, arc.y.col, 0);
// if(domains.get(arc.x).size() > 0 && board.meetsConstraints(arc.x.row, arc.x.col, domains.get(arc.x).get(0))){
// if(board.set(arc.x.row, arc.x.col, domains.get(arc.x).get(0)))moveCount++;
// }else{
// continue;
// }
if(!domains.keySet().contains(arc.x)){
System.out.println("Program terminated while analyzing "+arc.x.row+", "+arc.x.col);
return false;
}
// if(domains.get(arc.x).size() == 0 && board.get(arc.x.row, arc.x.col) == 0){
//// System.out.println("Program terminated while analyzing "+arc.x.row+", "+arc.x.col);
// for(Square s : domains.keySet()){
// if(domains.get(s).size() > 0)
// return AC3();
// }
// return false; // no solution
// }
for(Square k : board.getNeighbors(arc.x.row, arc.x.col)){
Arc newArc = new Arc(k, arc.x);
if(k != arc.x){
// board.set(arc.x.row, arc.x.col, 0);
// board.set(k.row, k.col, 0);
arcList.add(newArc);
}
}
}
}
return AC3();
// return true;
}
public static boolean revise(Square x, Square y){
boolean revised = false;
Iterator<Integer> it = domains.get(x).iterator();
while(it.hasNext()){
// for(Integer i : domains.get(x)){
int i = it.next();
if(!anyY(x, y)){
// domains.get(x).remove(i);
it.remove();
// if(removed.containsKey(x)){
// removed.get(x).add(i);
// }else{
// ArrayList<Integer> dom = new ArrayList<Integer>();
// dom.add(i);
// removed.put(x, dom);
// }
revised = true;
}
}
return revised;
}
// check if there are any available Y values satisfy constraints for x
public static boolean anyY(Square x, Square y){
ArrayList<Square> tmp = new ArrayList<Square>();
for(Integer i : domains.get(y)){
// System.out.println(i);
if(board.meetsConstraints(y.row, y.col, i)){
return true;
}
}
return false;
}
public static void printBoard(){
for(int i=0; i<9; i++){
for(int j=0; j<9; j++){
System.out.print(board.get(i,j)+" ");
if((j+1)%3 == 0) System.out.print(" ");
}
if((i+1)%3 == 0) System.out.println();
System.out.println();
}
}
public static void makeBoard(){
// Create new board:
Square[][] squares = new Square[9][9];
// Initialize
for(int i=0; i<9; i++){ // Rows
for(int j=0; j<9; j++){ // Columns
squares[i][j] = new Square(i, j, 0, false);
}
}
// Rows 0-2
squares[0][1].set(9);
squares[0][7].set(2);
squares[0][8].set(5);
squares[1][0].set(4);
squares[1][2].set(5);
squares[1][3].set(2);
squares[2][1].set(6);
squares[2][4].set(3);
// Rows 3-5
squares[3][0].set(2);
squares[3][1].set(8);
squares[3][3].set(3);
squares[3][6].set(1);
squares[3][8].set(9);
squares[4][3].set(8);
squares[4][5].set(1);
squares[5][0].set(3);
squares[5][2].set(7);
squares[5][5].set(6);
squares[5][7].set(4);
squares[5][8].set(8);
// Rows 6-8
squares[6][4].set(1);
squares[6][7].set(8);
squares[7][5].set(3);
squares[7][6].set(7);
squares[7][8].set(2);
squares[8][0].set(6);
squares[8][1].set(3);
squares[8][7].set(9);
// Rows 0-2
squares[0][1].setGiven();
squares[0][7].setGiven();
squares[0][8].setGiven();
squares[1][0].setGiven();
squares[1][2].setGiven();
squares[1][3].setGiven();
squares[2][1].setGiven();
squares[2][4].setGiven();
// Rows 3-5
squares[3][0].setGiven();
squares[3][1].setGiven();
squares[3][3].setGiven();
squares[3][6].setGiven();
squares[3][8].setGiven();
squares[4][3].setGiven();
squares[4][5].setGiven();
squares[5][0].setGiven();
squares[5][2].setGiven();
squares[5][5].setGiven();
squares[5][7].setGiven();
squares[5][8].setGiven();
// Rows 6-8
squares[6][4].setGiven();
squares[6][7].setGiven();
squares[7][5].setGiven();
squares[7][6].setGiven();
squares[7][8].setGiven();
squares[8][0].setGiven();
squares[8][1].setGiven();
squares[8][7].setGiven();
// Add values to board:
board = new Board(squares);
}
}