Euler #28

https://projecteuler.net/problem=28 => Number spiral diagonals

Los problemas en "2D" son siempre entretenidos. El problema es bastante sencillo, pero hay que tener cuidado y llevar un control de en qué dirección vamos y a cuándo "hay que torcer".

import sys

if len(sys.argv) != 2:
 print "Usage: 028.py <SIZE>"
 sys.exit()

table = []
size = int(sys.argv[1])
if size % 2 == 0:
 print "Only odd numbers"
 sys.exit()

for _ in range(0, size):
 row = []
 for _ in range(0, size):
  row.append(0)
 table.append(row)

directions = ((0,1), (1,0),(0,-1),(-1,0))

def get_next_direction(current): 
 i = directions.index(current)
 if i == len(directions) - 1:
  i = 0
 else:
  i += 1
 return directions[i]

max_num = size**2
x = size/2
y = size/2
diagonal_sum = 0
current_direction = (-1,0)
for a in range(1, max_num+1):
 if x == y or x + y == size - 1:
  diagonal_sum += a
 table[x][y] = a
 new_direction = get_next_direction(current_direction)
 x1 = x + new_direction[0]
 y1 = y + new_direction[1]
 if table[x1][y1] == 0:
  x, y = x1, y1
  current_direction = new_direction
 else:
  x, y = x + current_direction[0], y + current_direction[1]

#for row in table:
# print row
print "diagonal_sum", diagonal_sum