DPL_1_F: 0-1 Knapsack Problem II

問題へのリンク

C#のソース

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

class Program
{
    static string InputPattern = "InputX";

    static List<string> GetInputList()
    {
        var WillReturn = new List<string>();

        if (InputPattern == "Input1") {
            WillReturn.Add("4 5");
            WillReturn.Add("4 2");
            WillReturn.Add("5 2");
            WillReturn.Add("2 1");
            WillReturn.Add("8 3");
            //13
        }
        else if (InputPattern == "Input2") {
            WillReturn.Add("2 20");
            WillReturn.Add("5 9");
            WillReturn.Add("4 10");
            //9
        }
        else {
            string wkStr;
            while ((wkStr = Console.ReadLine()) != null) WillReturn.Add(wkStr);
        }
        return WillReturn;
    }

    struct ItemInfoDef
    {
        internal long Value;
        internal long Weight;
    }
    static List<ItemInfoDef> mItemInfoList = new List<ItemInfoDef>();

    static void Main()
    {
        List<string> InputList = GetInputList();

        long[] wkArr = { };
        Action<string> SplitAct = pStr =>
            wkArr = pStr.Split(' ').Select(pX => long.Parse(pX)).ToArray();

        SplitAct(InputList[0]);
        long WeightLimit = wkArr[1];

        foreach (string EachStr in InputList.Skip(1)) {
            SplitAct(EachStr);
            ItemInfoDef WillAdd;
            WillAdd.Value = wkArr[0];
            WillAdd.Weight = wkArr[1];
            mItemInfoList.Add(WillAdd);
        }

        long UB = mItemInfoList.Sum(pX => pX.Value);

        // 最小の重さ[価値合計]なインラインDP表
        long?[] DPArr = new long?[UB + 1];
        DPArr[0] = 0;

        foreach (ItemInfoDef EachItemInfo in mItemInfoList) {
            for (long I = UB; 0 <= I; I--) {
                if (DPArr[I].HasValue == false) continue;

                long NewKey = I + EachItemInfo.Value;
                long NewVal = DPArr[I].Value + EachItemInfo.Weight;
                if (NewVal > WeightLimit) continue;

                if (DPArr[NewKey].HasValue) {
                    if (DPArr[NewKey].Value <= NewVal) {
                        continue;
                    }
                }
                DPArr[NewKey] = NewVal;
            }
        }

        var AnswerList = new List<long>();
        for (long I = 0; I <= UB; I++) {
            if (DPArr[I].HasValue) {
                AnswerList.Add(I);
            }
        }
        Console.WriteLine(AnswerList.Max());
    }
}

解説

最小の重さ[価値合計]でインラインDPしてます。