题解 | #二叉树遍历#
二叉树遍历
https://www.nowcoder.com/practice/4b91205483694f449f94c179883c1fef
s = input()
stack = []#栈实现中序输出 ps：若是队列，则是中序
ans = []
for x in s:
if x != "#":
stack.append(x)
else:
if stack:
ans.append(stack.pop())
h = " ".join(ans) + " "
print(h)
