[백준] 1991번 트리 순회 python

n = int(input())
tree = {}

for _ in range(n):
    root, left, right = input().split()
    tree[root] = [left,right]

def preorder(a):
    if a is not '.':
        print(a,end='')
        preorder(tree[a][0])
        preorder(tree[a][1])

def inorder(a):
    if a is not '.':
        inorder(tree[a][0])
        print(a,end='')
        inorder(tree[a][1])

def postorder(a):
    if a is not '.':
        postorder(tree[a][0])
        postorder(tree[a][1])
        print(a,end='')

preorder('A')
print()
inorder('A')
print()
postorder('A')