solution to the heathrow route planning problem from learnyousomeerlang.com

heathrow.cs

using System;
using System.Collections.Generic;
using System.Linq;

namespace CSHeathrow
{
    class Program
    {
        static void Main(string[] args)
        {
            var init = new RoutePair(0, new List<string>(), 0, new List<string>() );

            Functions.CalcNewRoutePair(init, 50, 10, 30);

            var moveSteps = new List<MoveStep>
                                {
                                    new MoveStep(50, 10, 30),
                                    new MoveStep(5, 90, 20),
                                    new MoveStep(40, 2, 25),
                                    new MoveStep(10, 8, 0)
                                };

            var myResult = moveSteps.Aggregate(init,
                                (curState, curEntry) =>
                                Functions.CalcNewRoutePair(curState, curEntry.AFwd, curEntry.BFwd, curEntry.XCross));

            Console.WriteLine("A Value: {0}", myResult.AVal);
            Console.WriteLine("A Path: ");
            foreach (var str in myResult.AMoves)
            {
                Console.WriteLine(str);
            }
            Console.WriteLine();

            Console.WriteLine("B Value: {0}", myResult.BVal);
            Console.WriteLine("B Path: ");
            foreach (var str in myResult.BMoves)
            {
                Console.WriteLine(str);
            }
            Console.WriteLine();
        }
    }

    class MoveStep
    {
        public int AFwd { get; private set; }
        public int BFwd { get; private set; }
        public int XCross { get; private set; }

        public MoveStep(int aFwd, int bFwd, int xCross)
        {
            this.AFwd = aFwd;
            this.BFwd = bFwd;
            this.XCross = xCross;
        }
    }

    class RoutePair
    {
        public int AVal { get; private set ; }
        public List<string> AMoves { get; private set; }

        public int BVal { get; private set; }
        public List<string> BMoves { get; private set; }

        public RoutePair(int aVal, List<string> aMoves, int bVal, List<string> bMoves)
        {
            this.AVal = aVal;
            this.AMoves = aMoves;
            this.BVal = bVal;
            this.BMoves = bMoves;
        }
    }

    class Functions
    {
        public static RoutePair CalcNewRoutePair(RoutePair currentPair, int aVal, int bVal, int xCrossVal)
        {
            var valToAStraightFromA = currentPair.AVal + aVal;
            var valToACrossFromB = currentPair.BVal + bVal + xCrossVal;
            var newAVal = Math.Min(valToAStraightFromA, valToACrossFromB);

            List<string> newAMoves;
            if(valToAStraightFromA < valToACrossFromB)
            {
                newAMoves = new List<string>(currentPair.AMoves);   
                newAMoves.Add("AFwd");
            }
            else
            {
                newAMoves = new List<string>(currentPair.BMoves);
                newAMoves.Add("BFwd");
                newAMoves.Add("XCross");
            }

            //----------------------------------------------

            var valToBStraightFromB = currentPair.BVal + bVal;
            var valToBCrossFromA = currentPair.AVal + aVal + xCrossVal;
            var newBVal = Math.Min(valToBStraightFromB, valToBCrossFromA);

            List<string> newBMoves;
            if (valToBStraightFromB < valToBCrossFromA)
            {
                newBMoves = new List<string>(currentPair.BMoves);
                newBMoves.Add("BFwd");
            }
            else
            {
                newBMoves = new List<string>(currentPair.AMoves);
                newBMoves.Add("AFwd");
                newBMoves.Add("XCross");
            }

            return new RoutePair(newAVal, newAMoves, newBVal, newBMoves);
        }
    }
}