Same Tree

public class Solution {
    public boolean isSameTree(TreeNode p, TreeNode q) {
        if(p==null) return q==null;
        if(q==null) return p==null;
        if(p.val==q.val){
            return isSameTree(p.left,q.left)&&isSameTree(p.right,q.right);
        }
        else return false;
    }
}