Compare Two Binary Tree structures?

Question

Given 2 binary search tree what we know is -
1. Both the trees have same number of elements.
2. Elements can be same or different.
3. We need to find out if the structure of both the trees is same or not. (only structure not the content)

Answer 1

check at each level if the node exist or not and traverse completely.

private boolean sameStructure(TreeNode ref, TreeNode otherRef) 
{
    if (otherRef == null && ref != null)
        return false;
    if (otherRef != null && ref == null)
        return false;
    if (otherRef == null && ref == null)
        return true;

    return sameStructureHelp(ref.left, otherRef.left) && 
           sameStructureHelp(ref.right, otherRef.right);
}