100. 相同的树

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);
    }
}