``````# Randomly fills a grid of size 10 x 10 with digits between 0
# and bound - 1, with bound provided by the user.
# Given a point P of coordinates (x, y) and an integer "target"
# also all provided by the user, finds a path starting from P,
# moving either horizontally or vertically, in either direction,
# so that the numbers in the visited cells add up to "target".
# The grid is explored in a depth-first manner, first trying to mone north, always trying to keep the current direction,
# and if that does not work turning in a clockwise manner.
#
# Written by Eric Martin for COMP9021

import sys
from random import seed, randrange
from array_stack import *

dim = 10
grid = [ * dim for _ in range(dim)]

def display_grid():
for i in range(dim):
print('    ', end = '')
for j in range(dim):
print(' ', grid[i][j], end = '')
print()
print()

def explore_depth_first(x, y, target):
directions = {'N': (-1, 0),'S': (1, 0), 'E': (0, 1), 'W': (0, -1)}
next_directions = {'': ('W', 'S', 'E', 'N'),
'N': ('W', 'E', 'N'),
'S': ('E', 'W', 'S'),
'E': ('N', 'S', 'E'),
'W': ('S', 'N', 'W')}
states = ArrayStack()
states.push(([(x, y)], [grid[x][y]], ''))
while not states.is_empty():
path, sums, previous_direction = states.pop()
if sums[-1] == target:
return path
x, y = path[-1], path[-1]
for next_direction in next_directions[previous_direction]:
next_x, next_y = x + directions[next_direction],\
y + directions[next_direction],
if next_x not in range(dim) or next_y not in range(dim):
continue
if (next_x, next_y) in path:
continue
next_sum = sums[-1] + grid[next_x][next_y]
if next_sum > target:
continue
path_copy = list(path)
path_copy.append((next_x, next_y))
sums_copy = list(sums)
sums_copy.append(next_sum)
states.push((path_copy, sums_copy, next_direction))
return None

provided_input = input('Enter five integers: ').split()
if len(provided_input) != 5:
print('Incorrect input, giving up.')
sys.exit()
try:
seed_arg, bound, x, y, target = [int(x) for x in provided_input]
if bound < 1 or x < 0 or x > 9 or y < 0 or y > 9 or target < 0:
raise ValueError
except ValueError:
print('Incorrect input, giving up.')
sys.exit()

seed(seed_arg)
# We fill the grid with randomly generated digits between 0 and bound - 1.
for i in range(dim):
for j in range(dim):
grid[i][j] = randrange(bound)
print('Here is the grid that has been generated:')
display_grid()

path = explore_depth_first(x, y, target)
if not path:
print('There is no way to get a sum of {} starting '
'from ({}, {})'.format(target, x, y))
else:
print('With North as initial direction, and exploring '
'the space clockwise,\n'
'the path yielding a sum of {} starting from '
'({}, {}) is:\n {}'.format(target, x, y, path))

``````

Resource created Monday 12 October 2015, 09:35:10 AM.

file: quiz_8_solution.py