Summing values across nested lists at each index

问题

I have a List<List<string>> called _DataCollection where each of the nested lists have an equal number of values. Although all strings, the values in the nested lists will be strings consisting of alphanumeric characters, empty strings, or a currency value. For example

_DataCollection[0] = {"tom", "abc", "$525.34", "$123"}
_DataCollection[1] = {"dick", "xyz", "$100", "$234"}
_DataCollection[2] = {"harry", "", "$250.01", "$40"}
_DataCollection[2] = {"bob", "", "$250.01", ""}

What I need to do is come up with a way to sum all values per index across all the nested lists and add this to a list:

newSumList[0] = "N/A" since "tom" + "dick" + "harry" + "bob" can't be aggregated.
newSumList[1] = "N/A" since "abc" + "xyz" + "" + "" can't be aggregated.
newSumList[2] = "1125.36"
newSumList[3] = "397" even though the last value of the last nested list is "".

Basically, total all numeric values in nested lists for each index.

The only way I can think of is to iterate though these and keep a running total, but I was wondering if I can do it using LINQ or something else.

回答1:

Here you go.

var list = new List<List<string>>
{
    new List<string> {"tom", "abc", "$525.34", "$123"},
    new List<string> {"dick", "xyz", "$100", "$234"},
    new List<string> {"harry", "", "$250.01", "$40"},
    new List<string> {"bob", "", "$250.01", ""}
};

decimal num;
var itemsPerLine = list[0].Count; // 4
var res = list.SelectMany(line => line);
              .Select((s, i) => new { Text = s, Index = i })
              .GroupBy(i => i.Index % itemsPerLine) // transformed matrix here
              .Select(g => g.Sum(i => 
                   decimal.TryParse(i.Text, NumberStyles.AllowCurrencySymbol | 
                                            NumberStyles.AllowDecimalPoint, 
                                            new CultureInfo("en-US"), out num) 
                                            ? num : 0));

You can, of course, specify what should be recognized as a number by changing NumberStyles flags and culture info.

回答2:

Try this:-

decimal _temp =0;
int ListLength = _DataCollection.First().Count();
            var query = _DataCollection.SelectMany(x => x).
                                       Select((v, i) => new { Val = v, Index = i % ListLength })
                                       .GroupBy(x => x.Index)
                                       .Select(z => z.Sum(y => decimal.TryParse(y.Val,out _temp) ? _temp : 0));

Working Fiddle.

回答3:

Or, for a different approach that doesn't require rearranging the sequences with GroupBy:

        var culture = new CultureInfo("en-US");
        List<string> sums =
            _DataCollection.Count == 0
            ? new List<string>()
            : Enumerable.Range(0, _DataCollection.First().Count)
            .Select(i => _DataCollection.Select(list => list[i])
                       .Select(s => { decimal val; return string.IsNullOrEmpty(s) ? (decimal?)0 : decimal.TryParse(s, NumberStyles.Currency, culture, out val) ? (decimal?)val : (decimal?)null; })
                       .Aggregate((decimal?)0, (sum, val) => sum + val))
            .Select(sum => sum.HasValue ? sum.Value.ToString(culture) : "N/A")
            .ToList();

回答4:

List<List<string>> _DataCollection=new List<List<string>>();
            _DataCollection.Add( new List<string> {"tom", "abc", "$525.34", "$123"});

            _DataCollection.Add( new List<string> {"dick", "xyz", "$100", "$234"});
            _DataCollection.Add( new List<string> {"harry", "", "$250.01", "$40"});
            _DataCollection.Add( new List<string> {"bob", "", "$250.01", ""});

            List<string> newSumList = new List<string>();

            for (int i = 0; i < _DataCollection.Count; i++)
            {
                decimal Sum = 0;
                string CurrentSumList;
                string Comment;
                decimal amount = 0;
                for (int j = 0; j < _DataCollection.Count; j++)
                {
                    bool IsDecimalAmount=decimal.TryParse( _DataCollection[j][i].Replace('$','0'),out amount);
                    if (IsDecimalAmount)
                    {

                        Sum += amount;
                    }
                    else
                    {
                        Comment = "String";

                    }
                }
                CurrentSumList = Sum.ToString();
                newSumList.Add(CurrentSumList);
            }

I have implemented this & it gives me the Result.

回答5:

// Replace $value with value and remove all non-value strings
var dollars = _DataCollection
    .Select(l => l.Select(str => str.Contains('$') ? str.Split('$')[1] : string.Empty));

var newSumList = new List<double>();

// Add all values in a new list
for (int i = 0; i < _DataCollection[0].Count; i++)
{
    double toAdd = 0;
    foreach (var entry in dollars)
    {
        // If entry is a value, parse it, 0 otherwise
        var value = entry.ElementAt(i) != string.Empty ? double.Parse(entry.ElementAt(i)) : 0;
        toAdd = toAdd + value;
    }
    newSumList.Add(toAdd);
}
newSumList.ForEach(Console.WriteLine);

回答6:

without iterating multiple times and supporting empty source lists

var list = new List<string[]>
{
    new [] {"tom", "abc", "$525.34", "$123"},
    new [] {"dick", "xyz", "$100", "$234"},
    new [] {"harry", "", "$250.01", "$40"},
    new [] {"bob", "", "$250.01", ""}
};
var cutlure = new CultureInfo("en-US");
var result = list.Aggregate((decimal[])null, (sums, strings) =>
    {
        if (sums == null)
            sums = Enumerable.Repeat(decimal.MinValue, strings.Length).ToArray();
        for (int i = 0; i < strings.Length; i++)
        {
            decimal value;
            if (decimal.TryParse(strings[i], NumberStyles.Currency, cutlure, out value))
                sums[i] = (sums[i] == decimal.MinValue) ? value : sums[i] + value;
        }
        return sums;
    },
    sums => sums.Select(sum => (sum == decimal.MinValue) ? "N/A" : sum.ToString()).ToArray());

来源：https://stackoverflow.com/questions/26581670/summing-values-across-nested-lists-at-each-index