Issues with lists

Question

I am trying to work on HCF

I created a list with prime factors and I am trying to load the common factors

Parent=16 ,Number=2 , Cnts=4

Parent=48 ,Number=2 , Cnts=4

Parent=48 ,Number=3 , Cnts=1

Should give

Parent=16 ,Number=2 , Cnts=4

Parent=48 ,Number=2 , Cnts=4

As Number 2 exits between 2 parents.

Here is code snippet for Copilot it works well for one scenario it fail for another scenario

Parent=16 ,Number=2 , Cnts=4

Parent=48 ,Number=2 , Cnts=4

Parent=48 ,Number=3 , Cnts=1

Parent=7 ,Number=7 , Cnts=1

Here it should give empty result as parent 7 doesnt have number 2

public class Summary
{
    public int Parent { get; set; }
    public int Number { get; set; }
    public int Cnts { get; set; }
}
public class Program
{
    public static void Main(string[] args)
    {
        var summaries = new List<Summary>
        {
            new Summary { Parent = 16, Number = 2, Cnts = 4 },
            new Summary { Parent = 48, Number = 2, Cnts = 4 },
            new Summary { Parent = 48, Number = 3, Cnts = 1 },
            new Summary { Parent = 7, Number = 7, Cnts = 1 }
        };
        var filteredSummaries = summaries
            .GroupBy(s => s.Number)
            .Where(g => g.Select(s => s.Parent).Distinct().Count() > 1)
            .SelectMany(g => g)
            .ToList();
        Console.WriteLine("Filtered summaries:");
        foreach (var summary in filteredSummaries)
        {
            Console.WriteLine($"Parent: {summary.Parent}, Number: {summary.Number}, Cnts: {summary.Cnts}");
        }
        if (!filteredSummaries.Any())
        {
            Console.WriteLine("The list is empty.");
        }
    }
}
// Should give Empty 
//Where as Sample 2 
using System;
using System.Collections.Generic;
using System.Linq;
public class Summary
{
    public int Parent { get; set; }
    public int Number { get; set; }
    public int Cnts { get; set; }
}
public class Program
{
    public static void Main(string[] args)
    {
        var summaries = new List<Summary>
        {
            new Summary { Parent = 16, Number = 2, Cnts = 4 },
            new Summary { Parent = 48, Number = 2, Cnts = 4 },
            new Summary { Parent = 48, Number = 3, Cnts = 1 }, 
        };
        var filteredSummaries = summaries
            .GroupBy(s => s.Number)
            .Where(g => g.Select(s => s.Parent).Distinct().Count() > 1)
            .SelectMany(g => g)
            .ToList();
        Console.WriteLine("Filtered summaries:");
        foreach (var summary in filteredSummaries)
        {
            Console.WriteLine($"Parent: {summary.Parent}, Number: {summary.Number}, Cnts: {summary.Cnts}");
        }
        if (!filteredSummaries.Any())
        {
            Console.WriteLine("The list is empty.");
        }
    }
}
/*
should give 
Filtered summaries:
Parent: 16, Number: 2, Cnts: 4
Parent: 48, Number: 2, Cnts: 4
*/

Answer 1

Try an alternative:

var parents = summaries
    .Select( s => s.Parent )
    .Distinct( )
    .ToList( );
var filteredSummaries = summaries
    .Where( s => parents.All( p => summaries.Any( q => q.Parent == p && q.Number == s.Number ) ) )
    .ToList( );

Answer 2

I found some hits in Copilot finished the code

using System;
using System.Collections.Generic;
using System.Linq;
public class Summary
{
    public int Parent { get; set; }
    public int Number { get; set; }
    public int Cnts { get; set; }
}
     
public class Program
{
  
    public static void Main(string[] args)
    {
       
    var summaries = new List<Summary>
        {
            new Summary { Parent = 60, Number = 2, Cnts = 2 },
            new Summary { Parent = 60, Number = 3, Cnts = 1},
            new Summary { Parent = 60, Number = 5, Cnts = 1},
            new Summary { Parent = 90, Number = 2, Cnts = 1 },
            new Summary { Parent = 90, Number = 3, Cnts = 2},
            new Summary { Parent = 90, Number = 5, Cnts = 1} 
        };
        // Create a dictionary to group summaries by Parent and Number
        var newSummaries = new List<Summary>(summaries);
        // Count the number of newSummaries where Parent is not equal to summaries.Parent
        // Count the number of distinct parents in newSummaries where Parent is not equal to summaries.Parent and Number matches
       
        var filtergroups = new List<Summary>();
        foreach (var summary in summaries)
        {
            int count = 0; int countm = 0;
            var distinctNewParents = newSummaries
                .Where(ns => ns.Parent != summary.Parent)
                .Select(ns => ns.Parent)
                .Distinct();
            foreach (var parent in distinctNewParents)
            {
                count++;
            }
        
                           //
                           var distinctParentsmatch = newSummaries
                    .Where(ns => ns.Parent != summary.Parent && ns.Number == summary.Number)
                    .Select(ns => ns.Parent)
                    .Distinct();
            var distinctParents = new HashSet<int>();
            foreach (var parentx in distinctParentsmatch)
                {
                    distinctParents.Add(parentx);
                }
            countm = distinctParents.Count;
            if (count == countm)
            {
                filtergroups.Add(new Summary { Parent = summary.Parent, Number = summary.Number, Cnts = summary.Cnts });
            }
        }
        // Print the filtergroups
        if (filtergroups.Any())
        {
            Console.WriteLine("Filtered groups:");
            foreach (var fg in filtergroups)
            {
                Console.WriteLine($"Parent: {fg.Parent}, Number: {fg.Number}, Cnts: {fg.Cnts}");
            }
        }
        else
        {
            Console.WriteLine("The list is empty.");
        }
    }
    
}