Linq计算集合中列表的差异数

Question

我想计算集合中列表中的差异（或相似性）的数量。以下代码是for循环，它产生正确的结果，将每个其他记录与第一个记录进行比较。 有没有办法做得更好？有了Linq，也许？

public void Main(){
        _records = new ObservableCollection<Record>();
        _records.Add(new Record { Name = "Correct", Results = new List<string> { "A", "B","C" } , Score="100%"} );
        _records.Add(new Record { Name = "John", Results = new List<string> { "A", "B" ,"C" } } ); //Expect score to be 3/3  (100%)
        _records.Add(new Record { Name = "Joseph", Results = new List<string> { "A", "C","B" } }); //Expect score to be 2/3 (67%)
        _records.Add(new Record { Name = "James", Results = new List<string> { "C", "C", "C" } }); //Expect score to be 1/3 (33%)

        for(int i = 1; i < _records.Count(); i++) // Each Results in the _records except "Correct"
        {
            float score = _records[0].Results.Count();
            _records[i].Score = string.Format("{0:p1}", (score - CountDifferences(_records[i].Results, _records[0].Results) )  / score );
        }


}

private int CountDifferences(List<string> x, List<string> y)
{
    return (x.Zip(y, (a, b) => a.Equals(b) ? 0 : 1).Sum());
}

Answer 1

我会这样做：

var results =
    from r0 in _records.Take(1)
    from r in _records
    let score = (double)r0.Results.Count()
    let differences = CountDifferences(r.Results, r0.Results)
    select new { record = r, score = ((score - differences) / score).ToString("p1") };

foreach (var result in results)
{
    result.record.Score = result.score;
}

我愿意，hovever建议您没有.Score作为Record的属性，因为只有当您可以将一条记录与另一条记录进行比较时，分数才有效。这意味着如果您有三个单独的结果，如果您与其他两个中的任何一个进行比较，那么得分可能会有所不同。

所以我会建议：

public class Record
{
    public string Name;
    public List<string> Results;
    public double GetScore(Record benchmark)
    {
        var max = benchmark.Results.Count;
        var differences = benchmark.Results
            .Zip(this.Results, (a, b) => a == b)
            .Where(r => r == false)
            .Count();
        return ((double)max - differences) / max;
    }
}

然后只需执行此查询即可获得结果：

var results =
    from r0 in _records.Take(1)
    from r in _records
    select new
    {
        record = r,
        score = r.GetScore(r0).ToString("p1")
    };

这让我：

Answer 2

我将LINQ（带有lambda表达式）语句用于使用学生名称作为键和自定义类Record作为值的字典。然后将其与单独的列表进行比较，预期成绩。

List<string> expected = new List<string>(){"A", "B","C" };
Dictionary<string, Record> _records = new Dictionary<string, Record>();
_records["John"] = new Record { Name = "John", Results = new List<string> { "A", "B" ,"C" } } ;
_records["Joseph"]= new Record { Name = "Joseph", Results = new List<string> { "A", "C","B" } } ;
_records["James"] = new Record { Name = "James", Results = new List<string> { "C", "C", "C" } } ;

foreach(var v in _records){
    decimal count = v.Value.Results.Where((x,index) => expected[index]==x).Count()/(decimal)expected.Count();
    v.Value.Score = String.Format("{0:P0}",count);
}

foreach(var v in _records)
    Console.WriteLine("{0} {1}",v.Value.Name,v.Value.Score);