Given a binary tree, find the lowest common ancestor (LCA) of two given nodes in the tree.

According to the definition of LCA on Wikipedia: “The lowest common ancestor is defined between two nodes v and w as the lowest node in T that has both v and w as descendants (where we allow **a node to be a descendant of itself**).”

_______3______ / \ ___5__ ___1__ / \ / \ 6 _2 0 8 / \ 7 4

For example, the lowest common ancestor (LCA) of nodes `5`

and `1`

is `3`

. Another example is LCA of nodes `5`

and `4`

is `5`

, since a node can be a descendant of itself according to the LCA definition.

Show Similar Problems

/** * Definition for a binary tree node. * public class TreeNode { * int val; * TreeNode left; * TreeNode right; * TreeNode(int x) { val = x; } * } */ public class Solution { public TreeNode lowestCommonAncestor(TreeNode root, TreeNode p, TreeNode q) { if (root == null || root == p || root == q) return root; TreeNode l = lowestCommonAncestor(root.left, p, q); TreeNode r = lowestCommonAncestor(root.right, p, q); if (l != null && r != null) return root; if (l != null) return l; if (r != null) return r; // Need to have a return statement here. return null; } }

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