Leetcode236.java

// ----------------------------------------------------------------------------------------------
// LeetCode 236 : Lowest Common Ancestor of a Binary Tree 
// Link : https://leetcode.com/problems/lowest-common-ancestor-of-a-binary-tree/
// ----------------------------------------------------------------------------------------------

class Solution {
    public TreeNode lowestCommonAncestor(TreeNode root, TreeNode p, TreeNode q) {
        if (root.val == p.val || root.val == q.val)
            return root;

        if (root.left == null && root.right == null)
            return null;

        TreeNode left = null;
        TreeNode right = null;

        if (root.left != null)
            left = lowestCommonAncestor(root.left, p, q);
        if (root.right != null)
            right = lowestCommonAncestor(root.right, p, q);

        if (left != null && right != null) {
            return root;
        }

        return (left == null) ? right : left;
    }
}