knight's tour

knight.py

#!/usr/bin/python3

import argparse, sys, os, atexit
from ansi import cursor
from ansi.color import fg, bg, fx
from time import sleep

# manual fix for ansi.cursor.erase
from ansi.sequence import sequence
cursor.erase = sequence('2J')

parser = argparse.ArgumentParser(
    description='knight''s tour',
    formatter_class=argparse.ArgumentDefaultsHelpFormatter)
parser.add_argument('-w', '--width', type=int, default=5,
    help='width of board')
parser.add_argument('-a', '--height', type=int, default=0,
    help='height (altitude) of board; 0 means same as width')
parser.add_argument('-x', type=int, default=0,
    help='initial x position, 0 to width-1')
parser.add_argument('-y', type=int, default=0,
    help='initial y position, 0 to height-1')
parser.add_argument('-s', '--speed', type=int, default=12,
    help='speed; exponential effect; meaningful value roughly 0 to 18')
args = parser.parse_args()

if args.height <= 0:
    args.height = args.width
if args.x < 0 or args.x >= args.width:
    print('initial x position should be 0 to width-1')
if args.y < 0 or args.y >= args.height:
    print('initial y position should be 0 to height-1')
term = os.get_terminal_size()

def xy2rc(x, y):
    return (
        (term.lines - args.height*2)//2 + (args.height - y)*2,
        (term.columns - args.width*4)//2 + x*4
    )

def show_at(x, y, s, style=''):
    sys.stdout.write(str(style) + str(cursor.goto(*xy2rc(x, y))) + s + str(fx.reset))
    sys.stdout.flush()

board = [ [ 0 for y in range(args.height) ] for x in range(args.width) ]
move = ( (2,1), (1,2), (-1,2), (-2,1), (-2,-1), (-1,-2), (1,-2), (2,-1) )

def step(k, x, y):
    if x<0 or y<0 or x>=args.width or y>=args.height or board[x][y]>0:
        return False
    board[x][y] = k
    show_at(x, y, '{:3}'.format(k), style=fg.cyan+fx.negative)
    sleep(1.0/(1<<args.speed))
    show_at(x, y, '{:3}'.format(k))
    if k >= args.width*args.height: return True
    for d in range(8):
        if step(k+1, x+move[d][0], y+move[d][1]):
            return True
    board[x][y] = 0
    show_at(x, y, '{:3}'.format(k), style=fg.red+fx.negative)
    sleep(1.0/(1<<args.speed))
    show_at(x, y, ' '*3)
    return False

atexit.register(
    lambda: sys.stdout.write(cursor.show()+cursor.goto(term.lines, 1))
)
sys.stdout.write(cursor.erase()+cursor.hide())

step(1, args.x, args.y)