Same Tree

public boolean isSameTree(TreeNode p, TreeNode q) {
        // Start typing your Java solution below
        // DO NOT write main() function
        if(p == null && q == null) return true;
        if(p == null || q == null) return false;
       
        if(p.val == q.val){
            return isSameTree(p.left, q.left) &&
                   isSameTree(p.right, q.right);    
        }
        return false;
    }