def preorder_nonrec(t, proc):
if not callable(proc):
raise ValueError('proc must be a function')
s = SStack()
while t is not None and not s.is_empty():
while t is not None:
proc(t.data)
if t.right is not None:
s.push(t.right)
t = t.left
t = s.pop()
def postorder_nonrec(t, proc):
if not callable(proc):
raise ValueError('proc must be a function')
s = SStack()
while t is not None or not s.is_empty():
while t is not None:
s.push(t)
t = t.left if t.left is not None else t.right
t = s.pop()
proc(t.data)
if not s.is_empty() and s.top().left == t:
t = s.top().right
else:
t = None
def DFS_graph(graph, v0):
""" Depth-First Search graph """
vnum = graph.vertex_num()
visited = [0] * vnum
visited[v0] = 1
DFS_seq = [v0]
st = SStack()
st.push((0, graph.out_edge(v0)))
while not st.is_empty():
i, edges = st.pop()
if i < len(edges):
v, e = edges[i]
st.push((i + 1, edges))
if not visited[v]:
DFS_seq.append(v)
st.push((0, graph.out_edge(v)))
return DFS_seq
def maze_solver(maze, start, end):
""" Backtracking solution , based on stack"""
if start == end:
print(start)
return True
st = SStack()
mark(maze, start)
st.push((start, 0))
while not st.is_empty():
pos, nxt = st.pop()
for i in range(nxt, 4):
nextp = pos[0] + dirs[i][0], pos[1] + dirs[i][1]
if nextp == end:
return True
if passable(maze, nextp):
st.push((pos, i + 1))
mark(maze, nextp)
st.push((nextp, 0))
break
print('No path found.')