Tree Traversals

def solve(postorder, inorder):
    postorder = list(map(int, postorder.split(",")))
    inorder = list(map(int, inorder.split(",")))
    def build(post, ino):
        if not post:
            return None
        root = post[-1]
        idx = ino.index(root)
        return (root, build(post[:idx], ino[:idx]), build(post[idx:-1], ino[idx+1:]))
    tree = build(postorder, inorder)
    from collections import deque
    q = deque([tree])
    result = []
    while q:
        nd = q.popleft()
        if nd:
            result.append(nd[0])
            q.append(nd[1])
            q.append(nd[2])
    print(" ".join(map(str, result)))