Produces a valid FEN sequence for a chessboard of nxn size with n number of queens such that no queen is attacking another.
The FEN sequence (Forsyth–Edwards Notation) is valid because it does not hold color, king, en pessant, castling, or score rules. Simply placements of queens. Similarly, the fen increases in length depending on board size
- The x and y values of the initial queen are bound to the size of the board; both must be within range (0, size]
- The size of the board should be within range (2, 25]; Any size greater than 25 will incur performance penalties.
- Size defaults to 8
import queens
# initialize a new board of size 8 with an initial queen (3, 4)
chessboard = queens.Board(3, 4)
chessboard.display()
'''Output:
1 2 3 4 5 6 7 8
1 Q X X X X X X X
2 X X X X X X Q X
3 X X X Q X X X X
4 X X X X X Q X X
5 X X X X X X X Q
6 X Q X X X X X X
7 X X X X Q X X X
8 X X Q X X X X X
timed execution: 0.03s user 0.03s system 52% cpu 0.101 total
'''
print(chessboard.fen)
#>>> Q7/6Q1/3Q4/5Q2/7Q/1Q6/4Q3/2Q5
chessboard.scan(2, 3, size=15)
chessboard.display()
'''Output:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
1 Q X X X X X X X X X X X X X X
2 X X Q X X X X X X X X X X X X
3 X X X X Q X X X X X X X X X X
4 X Q X X X X X X X X X X X X X
5 X X X X X X X X X Q X X X X X
6 X X X X X X X X X X X Q X X X
7 X X X X X X X X X X X X X Q X
8 X X X Q X X X X X X X X X X X
9 X X X X X X X X X X X X Q X X
10 X X X X X X X X Q X X X X X X
11 X X X X X Q X X X X X X X X X
12 X X X X X X X X X X X X X X Q
13 X X X X X X Q X X X X X X X X
14 X X X X X X X X X X Q X X X X
15 X X X X X X X Q X X X X X X X
timed execution: 0.04s user 0.03s system 61% cpu 0.113 total
'''
print(chessboard.fen)
#>>> Q14/2Q12/4Q10/1Q13/9Q5/11Q3/13Q1/3Q11/12Q2/8Q6/5Q9/14Q/6Q8/10Q4/7Q7
chessboard.scan(6, 7, size=25)
'''Output:
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
1 Q X X X X X X X X X X X X X X X X X X X X X X X X
2 X X X Q X X X X X X X X X X X X X X X X X X X X X
3 X Q X X X X X X X X X X X X X X X X X X X X X X X
4 X X X X X X X Q X X X X X X X X X X X X X X X X X
5 X X Q X X X X X X X X X X X X X X X X X X X X X X
6 X X X X X X Q X X X X X X X X X X X X X X X X X X
7 X X X X X X X X X Q X X X X X X X X X X X X X X X
8 X X X X X X X X X X X X Q X X X X X X X X X X X X
9 X X X X X X X X X X X X X X Q X X X X X X X X X X
10 X X X X X X X X X X X X X X X X X X X Q X X X X X
11 X X X X X X X X X X X X X X X X X X X X X X X Q X
12 X X X X X X X X X X X X X X X X X X X X Q X X X X
13 X X X X X X X X X X X X X X X X X X X X X X X X Q
14 X X X X X X X X X X X X X X X X X X X X X Q X X X
15 X X X X Q X X X X X X X X X X X X X X X X X X X X
16 X X X X X X X X X X X X X X X X X X X X X X Q X X
17 X X X X X X X X X X X X X Q X X X X X X X X X X X
18 X X X X X X X X Q X X X X X X X X X X X X X X X X
19 X X X X X Q X X X X X X X X X X X X X X X X X X X
20 X X X X X X X X X X X Q X X X X X X X X X X X X X
21 X X X X X X X X X X X X X X X Q X X X X X X X X X
22 X X X X X X X X X X X X X X X X X Q X X X X X X X
23 X X X X X X X X X X Q X X X X X X X X X X X X X X
24 X X X X X X X X X X X X X X X X Q X X X X X X X X
25 X X X X X X X X X X X X X X X X X X Q X X X X X X
timed execution: 4.19s user 0.04s system 99% cpu 4.258 total
'''
print(chessboard.fen)
#>>> Q24/3Q21/1Q23/7Q17/2Q22/6Q18/9Q15/12Q12/14Q10/19Q5/23Q1/20Q4/24Q/21Q3/4Q20/22Q2/13Q11/8Q16/5Q19/11Q13/15Q9/17Q7/10Q14/16Q8/18Q6bool Board::scan(std::vector<std::vector<Point> > const& b, int x=0, int y=0){
if(x==queen.x) return scan(b, x+1); //skip the queen row
if(x>=size) return true; //if i >= size then a queen has been placed on every row
if(b[x][y].safe){ //verify the space is free
auto o = b; //store a copy of the current board
set(x, y); //attempt a queen set
if(scan(cb, x+1)) //recursively check the next line until a return condition is met
return true; //return true if the check succeeded
cb = o; //reset the board to the board prior to queen set and continue
}
if(y+1<size)
return scan(cb, x, y+1); //check the next point in the row
return false;
}