c#中列表中的对数和最大值

Question

A poker game card representation is like below

public class Card
{ 
    public string Rank { get; set; } 
    public int Value { get; set; }
    public char Suit { get; set; }
}

From a list of Cards, i have to find number of pairs and max. value from the pairs

Sample values

    [
    { "A" , 14, 'D' }
    { "A" , 14, 'H' }
    { "T" , 10, 'D' }
    { "T" , 10, 'S' } 
    { "5" , 5,  'S' } 
    ]  

In this case 2 pairs [ 1 pair of A and 1 pair of T and max value is 14 ]

Sample values

    [
    { "K" , 13, 'D' }
    { "K" , 13, 'H' }
    { "2" , 2, 'D' }
    { "T" , 10, 'S' } 
    { "5" , 5,  'S' } 
    ]  

In this case only 1 pair of K and max value is 13

I used below LINQ to find the number of pairs

    var pairs_list = hand
        .GroupBy(i => i.Rank)
        .Where(g => g.Count() > 1)
        .Select(g => g.Key);

Any way to get the value of highest pair with this linq Or can we make a single query to find no of pairs and max value from the pairs ifany

Answer 1

Any way to get the value of highest pair with this linq

You're really close with your code. You've already selected all the Ranks that are pairs in your hand, so all that's left to do is pick only the largest value.

You should, however, do the grouping based on the integer Value , rather than the string Rank , as it's easier to find the "larger value" with integers.

int largestPairRankInHand = hand
    .GroupBy(card => card.Value)
    .Where(g => g.Count() > 1)
    .Select(g => g.Key)
    .OrderByDescending(val => val)
    .FirstOrDefault();

The OrDefault is just in case there are no items in your hand.

Here's a fiddle example: https://dotnetfiddle.net/5Vo45H

Answer 2

 var result = hand
      .GroupBy(i => i.Rank)
      .Where(g => g.Count() > 1)
      .Select((g, i) => (value: g.First().Value, index: i + 1))
      .Aggregate((value: 0, count: 0), (p1, p2) => p1.value > p2.value ? (p1.value, p2.index) : (p2.value, p2.index));

 //// or
 //       var result = hand
 //      .GroupBy(i => i.Value)
 //      .Where(g => g.Count() > 1)
 //      .Select((g, i) => (value: g.Key, index: i + 1))
 //     .Aggregate((value: 0, count: 0), (p1, p2) => p1.value > p2.value ? (p1.value, p2.index) : (p2.value, p2.index));

Console.WriteLine($" Pair Count: {result.count}, Max Value: {result.value}");

Answer 3

You could add class Result like :

public class Result
{
    public int NoRanks { get; set; } 
    public int MaxValue { get; set; }
}

And change little your code like :

var pairsList = hand
    .GroupBy(card => card.Rank)
    .Where(g => g.Skip(1).Any())
    .Select(o => new { Rank = o.Key, Value = o.Max(v => v.Value) });

And Build the result by using Max function like :

Result result = new Result
{
    NoRanks = pairsList.Count(),
    MaxValue = pairsList.Max(o => o.Value)
};

Demo : https://dotnetfiddle.net/GitsRb

public static void Main()
{
    var hand = new Card[]
    {
        new Card { Rank = "A", Value = 9, Suit = 'D' },
        new Card { Rank = "A", Value = 10, Suit = 'H' },
        new Card { Rank = "T", Value = 12, Suit = 'D' },
        new Card { Rank = "T", Value = 13, Suit = 'S' },
        new Card { Rank = "5", Value = 5, Suit = 'S' },
    };
    
    var pairsList = hand
        .GroupBy(card => card.Rank)
        .Where(g => g.Skip(1).Any())
        .Select(o => new { Rank = o.Key, Value = o.Max(v => v.Value) });
    
    Result result = new Result
    {
        NoRanks  = pairsList.Count(),
        MaxValue = pairsList.Max(o => o.Value)
    };
    
    Console.WriteLine($"Ranks: {string.Join(",", result.NoRanks )} and max value : {result.MaxValue}");

}

public class Card
{
    public string Rank { get; set; } 
    public int Value { get; set; }
    public char Suit { get; set; }
}

public class Result
{
    public int NoRanks  { get; set; } 
    public int MaxValue { get; set; }
}

I hope you find this helpful.