二叉树最近公共父结点

给定结点p，结点q，根结点root，求p，q的最近公共父结点。

1. p，q位于root的两侧，---> root；

2. p，q同时位于root的左、右子树  ---> 左、右子树返回的非空值。

def LCA(root, p, q):
    if (root is None) or (root == p) or (root == q):
        return root
    left = LCA(root.left, p, q)
    right = LCA(root.right, p, q)
    # 位于root两侧
    if left and right:
        return root
    return left if left else right

测试

node1 = TreeNode(1)
node2 = TreeNode(2)
node3 = TreeNode(3)
node4 = TreeNode(4)
node5 = TreeNode(5)
node6 = TreeNode(6)
node7 = TreeNode(7)
root = node1
root.left = node2
root.right = node3
node2.right = node5
node2.left = node4
node3.right = node7
node3.left = node6

print(LCA(root, node3, node4).val)