两棵树是否完全相等

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