def trans_infix_suffix(line):
st = SStack()
exp = []
for x in token(line):
if x not in infix_operators:
exp.append(x)
elif st.is_empty() or x == '(':
st.push(x)
elif x == ')':
while not st.is_empty() and st.top() != '(':
st.append(st.pop())
if st.is_empty():
raise ValueError
st.pop()
else:
while (not st.is_empty() and property[st.top()] >= property[x]
): # 当top是*/，x是+-的时候，将top加入
exp.append(st.pop())
st.push(x)
while not st.is_empty():
if st.top() == '(':
raise ValueError
exp.append(st.pop())
return exp
def postorder_nonrec(t, proc):
s = SStack()
while t is not None or not s.is_empty():
while t is not None: # 下行，直到找到栈顶的两子数为空
s.push(t)
t = t.left if t.left is not None else t.ringt # 这里不用 try，如果t下面没有子树不会报错，而是None
# 看结点定义def __init__(self,dat,right=None,left=None)
t = s.pop()
proc(t.data)
if not s.is_empty() and s.top.left == t: # 如果t是现在栈顶的左子树
t = s.top().right
else:
t = None #
def preorder_elements(t):
s = SStack()
while t is not None or not s.is_empty():
while t is not None:
s.push(t.right)
yield t.data
t = t.left
t = s.pop()
def preorder_nonrec(t, proc):
s = SStack()
while t is not None or not s.is_empty():
while t is not None: # 直到左枝为空
proc(t.data)
s.push(t.right)
t = t.left
t = s.pop()
def norec_fact(n):
res = 1
st = SStack()
while n > 0:
st.push(n)
n -= 1
while not st.is_empty():
res *= st.pop()
return res
def maze_solve(maze, start, end):
if start == end:
print(start)
return
st = SStack()
mark(maze, start)
st.push((start, 0))
while not st.is_empty():
pos, nxt = st.pop()
for i in range(0, 4):
nexp = pos[0] + dirs[i][0], pos[1] + dirs[i][1]
if nexp == end:
print_path(end, pos, st)
elif passable(maze, nexp):
st.push((pos, i + 1))
mark(maze, pos)
st.push((nexp, 0))
break
print('no path')