lowest common ancestor of a binary tree

  Definition for a binary tree node.
  public class TreeNode {
      int val;
      TreeNode left;
      TreeNode right;
      TreeNode(int x) { val = x; }
  }
 /
class  {
    public TreeNode lowestCommonAncestor(TreeNode root, TreeNode p, TreeNode q) {
        if((root==null)||(root==p||root==q))
            return root;
        TreeNode left=lowestCommonAncestor(root.left,p,q);
        TreeNode right=lowestCommonAncestor(root.right,p,q);
        if((left!=null)&&(right!=null))
            return root;
        else
        {
            return left==null?right:left;
        }
    }
}