根据ID比较两个不同的列表

发布于 2025-02-03 08:45:48 字数 183 浏览 3 评论 0原文

我在这里要做的是，我正在尝试通过CustomerFavoriteRepository的ID找到文章。我有两个不同的列表（Arclelist，Favlist），并且正在比较列表的ID并将其添加到空数组（Favartlist）中。有人帮助我如何实现循环？我在循环中的“ favartlist.add（）”点上遇到错误，我不知道我必须在那里给出哪个值。谢谢

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情感失落者 2025-02-10 08:45:48

您问题的简单答案是您需要构造newCustomerFav，然后将其传递到add方法：

//this is what i tried 
for (final article in articleList) {
  for (final customArticle in customerFavList) {
    if (article.id == customArticle.articleId) {
      // The values are just for example - I'm not certain how
      // you mean to derive `id` or `like` for a NewCustomerFav.
      final fav = NewCustomerFav(0, article, 1);
      customFavartList.add(fav);
    }
  }
}

在其他注意事项上，您的算法可以在此处进行改进 - 右现在，它将按照n * m操作的顺序来构建customfavartlist，其中n是文章的数量，m是收藏夹的数量。

可以减少它，以便算法在N + M的顺序上执行，而在有很多文章时，该算法的扩展会更好，并且客户有许多收藏夹。

这样做的方法是从FairitesList创建ID的set，类似的是：

// Assuming customerFavList is a list of int ids
final customerFavIdSet = Set.from(customerFavList.map((e) => e.articleId));

for (final article in articleList) {
  // Now you can check whether the article is a favorite with this one
  // query, rather than searching the whole list.
  if (customerFavIdSet.contains(article.id) {
    final fav = NewCustomerFav(0, article, 1);
    customFavartList.add(fav);
  }
}

The simple answer to your question is that you need to construct the NewCustomerFav, and pass it to the add method:

//this is what i tried 
for (final article in articleList) {
  for (final customArticle in customerFavList) {
    if (article.id == customArticle.articleId) {
      // The values are just for example - I'm not certain how
      // you mean to derive `id` or `like` for a NewCustomerFav.
      final fav = NewCustomerFav(0, article, 1);
      customFavartList.add(fav);
    }
  }
}

On a different note, your algorithm can be improved here - Right now it will take on the order of n * m operations to build customFavartList, where n is the number of articles, and m is the number of favorites.

It can be reduced so that the algorithm performs on the order of n + m, instead, which will scale much better when there are many articles, and the customer has many favorites.

The way to do it is to create a Set of ids from the favoritesList, something like this:

// Assuming customerFavList is a list of int ids
final customerFavIdSet = Set.from(customerFavList.map((e) => e.articleId));

for (final article in articleList) {
  // Now you can check whether the article is a favorite with this one
  // query, rather than searching the whole list.
  if (customerFavIdSet.contains(article.id) {
    final fav = NewCustomerFav(0, article, 1);
    customFavartList.add(fav);
  }
}

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