ALDS1_4_D: Allocation

問題へのリンク

C#のソース

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

// Q014 二分探索と貪欲法 https://judge.u-aizu.ac.jp/onlinejudge/description.jsp?id=ALDS1_4_D&lang=jp
class Program
{
    static string InputPattern = "InputX";

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

        if (InputPattern == "Input1") {
            WillReturn.Add("5 3");
            WillReturn.Add("8");
            WillReturn.Add("1");
            WillReturn.Add("7");
            WillReturn.Add("3");
            WillReturn.Add("9");
            //10
        }
        else if (InputPattern == "Input2") {
            WillReturn.Add("4 2");
            WillReturn.Add("1");
            WillReturn.Add("2");
            WillReturn.Add("2");
            WillReturn.Add("6");
            //6
        }
        else {
            string wkStr;
            while ((wkStr = Console.ReadLine()) != null) WillReturn.Add(wkStr);
        }
        return WillReturn;
    }

    static long mK;
    static long[] mWeightArr;

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

        long[] wkArr = InputList[0].Split(' ').Select(X => long.Parse(X)).ToArray();
        mK = wkArr[1];
        mWeightArr = InputList.Skip(1).Select(X => long.Parse(X)).ToArray();

        //二分法で解く
        long L = 0;
        long R = int.MaxValue;
        long Mid = (L + R) / 2;
        while (L + 1 < R) {
            //Console.WriteLine("L={0},Mid={1},R={2}", L, Mid, R);
            if (CanTousai(Mid)) {
                R = Mid;
            }
            else {
                L = Mid;
            }
            Mid = (L + R) / 2;
        }
        Console.WriteLine(R);
    }

    // 最大積載量Pを引数として、全ての荷物を搭載可能かを返す
    static bool CanTousai(long pP)
    {
        if (mWeightArr.Max() > pP) {
            return false;
        }

        long CurrSum = 0;
        long TrackCnt = 1;
        for (int I = 0; I <= mWeightArr.GetUpperBound(0); I++) {
            if (CurrSum + mWeightArr[I] > pP) {
                CurrSum = mWeightArr[I];
                TrackCnt++;
                if (TrackCnt > mK) {
                    return false;
                }
            }
            else {
                CurrSum += mWeightArr[I];
            }
        }
        return true;
    }
}

解説

二分探索と貪欲法を、組み合わせてます。