Re: [閒聊] 每日leetcode

[DJYOMIYAHINA (通通打死)]

肥肥翹班打code
先寫了稍微浪費一點點空間慢一點的版本
看到討論區標題之後 再寫了個好像快一點的版本
雖然複雜度都一樣就是


def createBinaryTree(self, descriptions: List[List[int]]) ->
Optional[TreeNode]:
    g = defaultdict(lambda: [-1,-1])
    childs = set()
    for d in descriptions:
        if d[2] == 1:
            g[d[0]][0] = d[1]
        else:
            g[d[0]][1] = d[1]
        childs.add(d[1])

    root = -1
    for node in g.keys():
        if node not in childs:
            root = node
            break

    def build(val) -> TreeNode:
        if val == -1:
            return None
        return TreeNode(val, build(g[val][0]), build(g[val][1]))

    return build(root)



def createBinaryTree(self, descriptions: List[List[int]]) ->
Optional[TreeNode]:
    nodes = {}
    childs = set()
    for d in descriptions:
        if d[0] not in nodes:
            nodes[d[0]] = TreeNode(d[0])
        if d[1] not in nodes:
            nodes[d[1]] = TreeNode(d[1])
        if d[2] == 1:
            nodes[d[0]].left = nodes[d[1]]
        else:
            nodes[d[0]].right = nodes[d[1]]

        childs.add(d[1])

    for node in nodes.keys():
        if node not in childs:
            return nodes[node]

    return None

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