using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

public class Program

{

    public static void Main()

    {

            var peoplesAwaitingValidation =

                new List<People> {

                    new People{ id = 1 , externalId = "A" },

                    new People{ id = 2 , externalId = "B" },

                    new People{ id = 3 , externalId = "C" },

                    new People{ id = 4 , externalId = "D" },

                    new People{ id = 5 , externalId = "E" },

                    new People{ id = 6 , externalId = "F" },

                };

​

            var relationsAwaitingValidation =

                new List<Relation> {

                    new Relation{ id = 1 , sourceExternalId = "A", destExternalId = "B" },

                    new Relation{ id = 2 , sourceExternalId = "A", destExternalId = "C" },

                    new Relation{ id = 3 , sourceExternalId = "A", destExternalId = "D" },

                    new Relation{ id = 4 , sourceExternalId = "E", destExternalId = "A" },

                    new Relation{ id = 3 , sourceExternalId = "E", destExternalId = "B" }

                };

​

            //Expected result :

            var orderedPeoplesAwaitingValidation = new List<People> {

                                                                // Weight

                    new People{ id = 5 , externalId = "E" },    // 0 = Lower level

                    new People{ id = 5 , externalId = "F" },    // 0

                    new People{ id = 1 , externalId = "A" },    // 1 

                    new People{ id = 3 , externalId = "C" },    // 2

                    new People{ id = 4 , externalId = "D" },    // 2

                    new People{ id = 2 , externalId = "B" },    // 3

                };

​

            // Graphical representation:

            // 1        2        3   Weight

            // E  --->  A  --->  B

            //             --->  C

            //             --->  D

            //    --->  B

​

            // F=0

​

            // Dict to Weight table

            var step1 = peoplesAwaitingValidation

                            .GroupBy(g => g.externalId)

                            .ToDictionary(

                                g =>   g.Key,

                                g =>   0

                            );

​

            var step2 = relationsAwaitingValidation

                            .Select(x => x.sourceExternalId)

                            .Distinct()

                            .ToList();

​

            var step3 = relationsAwaitingValidation

                            .GroupBy(g => g.sourceExternalId)

                            .Select(g => new

                            {

                                destExternalId = g.Key,

                                group = g.Select(x => x.destExternalId).ToList()

                            })

                            .ToList();

​

            int breakpoint = 0;

​

            for (int i = 0; i < step2.Count(); i++) {

                var source = step2[i];

                    step1[source]++;                

            }

​

            for (int i = 0; i<step3.Count(); i++) {

                var item = step3[i];

                foreach (var dest in item.group) {

                    step1[dest]=step1[dest]+2;          

                }

            }

​

            breakpoint = 0;

    }

    internal class People

    {

        public int id;

        public string externalId;

        public string postalInformation;

    }

​

    internal class Relation

    {

        public int id;

        public int type;

        public string sourceExternalId;

        public string destExternalId;

    }

}