Initial data commit

Task/Knights-tour/Python/knights-tour.py

@@ -0,0 +1,65 @@
+import copy
+
+boardsize=6
+_kmoves = ((2,1), (1,2), (-1,2), (-2,1), (-2,-1), (-1,-2), (1,-2), (2,-1))
+
+
+def chess2index(chess, boardsize=boardsize):
+    'Convert Algebraic chess notation to internal index format'
+    chess = chess.strip().lower()
+    x = ord(chess[0]) - ord('a')
+    y = boardsize - int(chess[1:])
+    return (x, y)
+
+def boardstring(board, boardsize=boardsize):
+    r = range(boardsize)
+    lines = ''
+    for y in r:
+        lines += '\n' + ','.join('%2i' % board[(x,y)] if board[(x,y)] else '  '
+                                 for x in r)
+    return lines
+
+def knightmoves(board, P, boardsize=boardsize):
+    Px, Py = P
+    kmoves = set((Px+x, Py+y) for x,y in _kmoves)
+    kmoves = set( (x,y)
+                  for x,y in kmoves
+                  if 0 <= x < boardsize
+                     and 0 <= y < boardsize
+                     and not board[(x,y)] )
+    return kmoves
+
+def accessibility(board, P, boardsize=boardsize):
+    access = []
+    brd = copy.deepcopy(board)
+    for pos in knightmoves(board, P, boardsize=boardsize):
+        brd[pos] = -1
+        access.append( (len(knightmoves(brd, pos, boardsize=boardsize)), pos) )
+        brd[pos] = 0
+    return access
+
+def knights_tour(start, boardsize=boardsize, _debug=False):
+    board = {(x,y):0 for x in range(boardsize) for y in range(boardsize)}
+    move = 1
+    P = chess2index(start, boardsize)
+    board[P] = move
+    move += 1
+    if _debug:
+        print(boardstring(board, boardsize=boardsize))
+    while move <= len(board):
+        P = min(accessibility(board, P, boardsize))[1]
+        board[P] = move
+        move += 1
+        if _debug:
+            print(boardstring(board, boardsize=boardsize))
+            input('\n%2i next: ' % move)
+    return board
+
+if __name__ == '__main__':
+    while 1:
+        boardsize = int(input('\nboardsize: '))
+        if boardsize < 5:
+            continue
+        start = input('Start position: ')
+        board = knights_tour(start, boardsize)
+        print(boardstring(board, boardsize=boardsize))