如何从交易数据中返回最佳 N 个客户的客户 ID

Question

我有一个 CSV 格式的交易数据，其中包含 Customer ID, Transaction Amount, Transaction Date 列。我有一个接受transactions_csv_file_path as string, N as an integer as params. I want to return the best N customers from the transaction data. NOTE:[最好的客户作为连续每日付款时间最长的客户]`的功能。我可以读取 CSV 如下：

public static string[,] ProcessCSV(string file_path, int n)
{
List<string> transData = new List<string>();
            using (StreamReader sr = new StreamReader(file_path))
            {
                
                string strResult = sr.ReadToEnd();
                var values = strResult.Split(',');
                transData.Add(values[0]);
                transData.Add(values[1]);

            }
return transData.ToArray();
}

调试时，我只得到没有数据的列标题。我想按日期获取每日连续付款并返回customerIds，例如：如果N=1，我希望输出为['K20008']，如果N=3, output: ['K20987', 'K20008', 'K20233']

如何从 CSV 中获取数组数据，并获得最佳的 N 个客户 ID 以及最长的连续每日付款时间？

考虑：define consecutive daily payments as at least 1 transaction per calendar day. and If there are any ties, use ascending order to break ties. For example, K20003 comes before K20005

Answer 1

我也许会做一个计算最长运行长度的方法：

int MaxRun(IEnumerable<DateTime> ds){
  int max = 0;
  int current = 0;
  var prev = DateTime.MinValue;

  foreach(var d in ds.Distinct().OrderBy(x => x)){
    if((d - prev).Days == 1)
      current++;
    else 
      current = 0;
    prev = d;
    if(current > max)
      max = current;
  }
  return max;
}

然后使用一点 LINQ 对人员进行分组，计算 maxrun，按 maxrun 排序转换，然后输出人员：

transactions
  .GroupBy(t => t.Customer, t => t.TransactionDate )
  .Select(g => new { g.Key, MR = MaxRun(g) })
  .OrderBy(at => at.MR)
  .ThenBy(at => at.Key)
  .Select(at => at.Key)
  .ToArray()