Question

我正在尝试编写自定义比较器，以根据相似性对搜索结果列表进行排序。我希望最喜欢输入的搜索词的术语首先出现在列表中，然后是以搜索词组开头的短语，然后是按字母顺序排列的所有其他值。

鉴于此测试代码：

  string searchTerm = "fleas";
  List<string> list = new List<string>
                                       {
                                           "cat fleas",
                                           "dog fleas",
                                           "advantage fleas",
                                           "my cat has fleas",
                                           "fleas",
                                           "fleas on my cat"
                                       };

我正在尝试使用此Comparer：

public class MatchComparer : IComparer<string>
{
    private readonly string _searchTerm;

    public MatchComparer(string searchTerm)
    {
        _searchTerm = searchTerm;
    }

    public int Compare(string x, string y)
    {
        if (x.Equals(_searchTerm) ||
             y.Equals(_searchTerm))
            return 0;

        if (x.StartsWith(_searchTerm) ||
            y.StartsWith(_searchTerm))
            return 0;

        if (x.Contains(_searchTerm))
            return 1;

        if (y.Contains(_searchTerm))
            return 1;

        return x.CompareTo(y);
    }

调用list.Sort（新的MatchComparer（searchTerm）会导致列表顶部的'我的猫有跳蚤'。

我想我必须在这里做一些奇怪/奇怪的事情......这里有什么问题或者我正在尝试做什么更好的方法？

谢谢！

Answer 1

您没有使用CompareTo的所有可能返回值

首先是

-1 == x 0 ==相等 1 == y first

你想要更像这样的东西

public class MatchComparer : IComparer<string> 
{ 
    private readonly string _searchTerm; 

    public MatchComparer(string searchTerm) 
    { 
        _searchTerm = searchTerm; 
    } 

    public int Compare(string x, string y) 
    { 
        if (x.Equals(y)) return 0; // Both entries are equal;
        if (x.Equals(_searchTerm)) return -1; // first string is search term so must come first
        if (y.Equals(_searchTerm)) return 1; // second string is search term so must come first
        if (x.StartsWith(_searchTerm)) {
            // first string starts with search term
            // if second string also starts with search term sort alphabetically else first string first
            return (y.StartsWith(_searchTerm)) ? x.CompareTo(y) : -1;
        }; 
        if (y.StartsWith(_searchTerm)) return 1; // second string starts with search term so comes first
        if (x.Contains(_searchTerm)) {
            // first string contains search term
            // if second string also contains the search term sort alphabetically else first string first
            return (y.Contains(_searchTerm)) ? x.CompareTo(y) : -1; 
        }
        if (y.Contains(_searchTerm)) return 1; // second string contains search term so comes first
        return x.CompareTo(y); // fall back on alphabetic
    } 
}

针对参数失败的自定义比较器

1 个答案: