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#!/usr/bin/env python3
import re
import sys
def convert_coord_to_list(coord: str) -> list:
letters = ' abcdefgh'
return (letters.index(coord[0]), int(coord[1]))
def knights_move(start_coord: str, end_coord: str) -> int:
'''Calculate the least number of knight moves between two positions'''
# Check if the position is valid
for coord in (start_coord, end_coord):
if not re.search('^[a-h][1-8]$', coord):
raise ValueError(
f'The position {coord} is not a valid chess coordinate!')
# Direction the knight piece can move
deltas = ([2, 1], [2, -1], [-2, 1], [-2, -1],
[1, 2], [1, -2], [-1, 2], [-1, -2])
# Where we start
coords = [convert_coord_to_list(start_coord)]
# Where we want to end
target = convert_coord_to_list(end_coord)
# Count the required moves
moves = 1
# Co-ordinates we've already been to
seen = []
while True:
# The new coordinates after we've made the next move
new_coords = []
# For all existing places after the previous move
for coord in coords:
# Move the knight in all possible ways
for delta in deltas:
new_pos = (coord[0] + delta[0], coord[1] + delta[1])
# But exclude moves that take it off the board or we've already used
if not 0 < new_pos[0] < 9 or not 0 < new_pos[1] < 9 or new_pos in seen:
continue
if new_pos == target:
# We've hit the target position
return moves
new_coords.append(new_pos)
seen.append(new_pos)
# Looks like we'll need to move again!
coords = new_coords
moves += 1
def main():
result = knights_move(sys.argv[1], sys.argv[2])
print(result)
if __name__ == '__main__':
main()
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