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Diffstat (limited to 'low_common_ancestor_leaf.py')
-rw-r--r-- | low_common_ancestor_leaf.py | 48 |
1 files changed, 48 insertions, 0 deletions
diff --git a/low_common_ancestor_leaf.py b/low_common_ancestor_leaf.py new file mode 100644 index 0000000..4b0036f --- /dev/null +++ b/low_common_ancestor_leaf.py @@ -0,0 +1,48 @@ +# 1123. Lowest Common Ancestor of Deepest Leaves +import leetcode + +""" +given the 'root' of a binary tree, return the lowest common ancestor of its +deepest leaves. recall that the node of a binary tree is a leaf if and only +if it has no children, the depth of the root of the tree is 0. if the depth +of a node is 'd', the depth of each of its children is 'd + 1'. and the +lowest common ancestor of a set 's' is the node 'a' with the largest depth +such that every node in 's' is in the subtree with root 'a'. +""" + + +class Solution(object): + def lcaDeepestLeaves(self, root): + """ + :type root: Optional[TreeNode] + :rtype: Optional[TreeNode] + """ + + def depth(node): + if not node: + return 0 + return max(depth(node.left), depth(node.right)) + 1 + + def dfs(node, m, n): + if not node: + return None + if m - 1 == n: + return node + l = dfs(node.left, m, n + 1) + r = dfs(node.right, m, n + 1) + if l and r: + return node + return l if l else r + + m = depth(root) + return dfs(root, m, 0) + + +if __name__ == "__main__": + obj = Solution() + r1 = leetcode.treenode_build(root=[3, 5, 1, 6, 2, 0, 8, None, None, 7, 4]) + r2 = leetcode.treenode_build(root=[1]) + r3 = leetcode.treenode_build(root=[0, 1, 3, None, 2]) + print(obj.lcaDeepestLeaves(r1)) + print(obj.lcaDeepestLeaves(r2)) + print(obj.lcaDeepestLeaves(r3)) |