Permalink
Find file
Fetching contributors…
Cannot retrieve contributors at this time
93 lines (74 sloc) 2.46 KB
# -----------
# User Instructions:
#
# Modify the the search function so that it becomes
# an A* search algorithm as defined in the previous
# lectures.
#
# Your function should return the expanded grid
# which shows, for each element, the count when
# it was expanded or -1 if the element was never expanded.
#
# Your function only needs to work for a 5x6 grid.
# You do not need to modify the heuristic.
# ----------
grid = [[0, 1, 0, 0, 0, 0],
[0, 1, 0, 0, 0, 0],
[0, 1, 0, 0, 0, 0],
[0, 1, 0, 0, 0, 0],
[0, 0, 0, 0, 1, 0]]
heuristic = [[9, 8, 7, 6, 5, 4],
[8, 7, 6, 5, 4, 3],
[7, 6, 5, 4, 3, 2],
[6, 5, 4, 3, 2, 1],
[5, 4, 3, 2, 1, 0]]
init = [0, 0]
goal = [len(grid)-1, len(grid[0])-1]
delta = [[-1, 0 ], # go up
[ 0, -1], # go left
[ 1, 0 ], # go down
[ 0, 1 ]] # go right
delta_name = ['^', '<', 'v', '>']
cost = 1
# ----------------------------------------
# modify code below
# ----------------------------------------
def search():
closed = [[0 for row in range(len(grid[0]))] for col in range(len(grid))]
closed[init[0]][init[1]] = 1
expand = [[-1 for row in range(len(grid[0]))] for col in range(len(grid))]
action = [[-1 for row in range(len(grid[0]))] for col in range(len(grid))]
x = init[0]
y = init[1]
g = 0
open = [[g, x, y]]
found = False # flag that is set when search is complet
resign = False # flag set if we can't find expand
count = 0
while not found and not resign:
if len(open) == 0:
resign = True
else:
open.sort()
open.reverse()
next = open.pop()
x = next[1]
y = next[2]
g = next[0]
expand[x][y] = count
count += 1
if x == goal[0] and y == goal[1]:
found = True
else:
for i in range(len(delta)):
x2 = x + delta[i][0]
y2 = y + delta[i][1]
if x2 >= 0 and x2 < len(grid) and y2 >=0 and y2 < len(grid[0]):
if closed[x2][y2] == 0 and grid[x2][y2] == 0:
g2 = g + cost + heuristic[x2][y2]
open.append([g2, x2, y2])
closed[x2][y2] = 1
for i in range(len(expand)):
print expand[i]
return expand #Leave this line for grading purposes!
search()