We compare the roots and then recursively compare their left and right subtrees.

1. If both p and q are None, they are the same (True).
2. If only one is None or their values differ, they are not the same (False).
3. Return is_same_tree(p.left, q.left) and is_same_tree(p.right, q.right).

• Time Complexity: O(N).
• Space Complexity: O(H).

def is_same_tree(p, q):
    if not p and not q:
        return True
    if not p or not q or p.val != q.val:
        return False
        
    return is_same_tree(p.left, q.left) and is_same_tree(p.right, q.right)