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如何删除列表中的每个n项,直到列表中。计数超过目标值?

for-loop linq list c#

-1

mr_blond · 技术社区 · 7 年前

有一张短名单。它的价值并不重要,比如:

List<short> resultTemp = new List<short>{1,2,3,4,5,6,7,8,9...};

此代码应该通过从结果列表中删除每个第n项来减少结果列表计数。

例1:

List<short>{1,2,3,4,5,6,7,8,9,10}.Count == 10;
var targetItemsCount = 5;

结果应为1,3,5,7,9且结果。计数应为==5

例2:

List<short>{1,2,3,4,5,6,7,8,9}.Count == 9;
var targetItemsCo:nt = 3;

结果应为1,4,7且结果。计数应为==3

但它应该停止删除它,在某个地方使结果计数等于targetItemsCount(在这段代码中是42,但它的其他值并不重要)。代码是:

var currentItemsCount = resultTemp.Count;

var result = new List<short>();

var targetItemsCount = 42;
var counter = 0;
var counterResettable = 0;

if (targetItemsCount < currentItemsCount)
{
    var reduceIndex = (double)currentItemsCount / targetItemsCount;

    foreach (var item in resultTemp)
    {
        if (counterResettable < reduceIndex || 
            result.Count + 1 == currentItemsCount - counter)
        {
            result.Add(item);
            counterResettable++;
        }
        else
        {
            counterResettable = 0;
        }
        counter++;
    }
}

在本例中,result.count等于41,但应为==TargetItemsCount==42;

我该如何删除列表中的每一个n项,直到全部删除。用c比目标值多计数?

3 回复 | 直到 7 年前

vc 74 7 年前

double increment = Convert.ToDouble(resultTemp.Count) / targetItemsCount;

List<short> result = Enumerable.Range(0, targetItemsCount).
                                Select(x => resultTemp[(int)(x * increment)]).
                                ToList();

List<short>{1,2,3,4,5,6,7,8,9}.Count == 9;
var targetItemsCount = 6;

[1, 2, 4, 5, 7, 8]

targetItemsCount > 0 targetItemsCount < resultTemp.Count

Link to Fiddle

xdtTransform 7 年前

public static void run()
{
    var inputs =
        new List<Input>{
          new Input{ 
              Value = new List<int> { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 },`
              TargetCount = 5, ExpectedOutput= new List<int>{1,3,5,7,9} 
          },
          new Input{  
              Value = new List<int> { 1, 2, 3, 4, 5, 6, 7, 8, 9 },
              TargetCount = 3, ExpectedOutput= new List<int>{1,4,7} 
          },
        };

    foreach (var testInput in inputs)
    {
        Console.WriteLine($"# Input = [{string.Join(", ", testInput.Value)}]");
        var result = Reduce(testInput.Value, testInput.TargetCount);
        Console.WriteLine($"# Computed Result = [{string.Join(", ", result)} ]\n");
    }
}

static List<int> Reduce(List<int> input, int targetItemsCount)
{
    while (input.Count() > targetItemsCount)
    {
        var nIndex = input.Count() / targetItemsCount;
        input = input.Where((x, i) => i % nIndex == 0).ToList();
    }
    return input;
}

class Input
{
    public List<int> ExpectedOutput;
    public List<int> Value;
    public int TargetCount;
}

Rand Random 7 年前

var resultTemp = Enumerable.Range(1, 9).ToList();
var targetItemsCount = 3;

var roundingError = resultTemp.Count % targetItemsCount;
var reduceIndex   = (resultTemp.Count - roundingError) / targetItemsCount;

List<int> result;
if (reduceIndex <= 1)
    result = resultTemp.Take(targetItemsCount).ToList();
else
    result = resultTemp.Where((a, index) => index % reduceIndex == 0).Take(targetItemsCount).ToList();

42 1 100 2nd 83