[leetcode] problem 236 – lowest common ancestor of a binary tree

public class  {
    int val;
    TreeNode left;
    TreeNode right;
    TreeNode(int x) { val = x; }
}

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

    TreeNode left = lowestCommonAncestor(root.left, p, q);        
    TreeNode right = lowestCommonAncestor(root.right, p, q);

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

    return left == null ? right : left;
}