ABC334-D Reindeer and Sleigh

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 3");
            WillReturn.Add("5 3 11 8");
            WillReturn.Add("16");
            WillReturn.Add("7");
            WillReturn.Add("1000");
            //3
            //1
            //4
        }
        else if (InputPattern == "Input2") {
            WillReturn.Add("6 6");
            WillReturn.Add("1 2 3 4 5 6");
            WillReturn.Add("1");
            WillReturn.Add("2");
            WillReturn.Add("3");
            WillReturn.Add("4");
            WillReturn.Add("5");
            WillReturn.Add("6");
            //1
            //1
            //2
            //2
            //2
            //3
        }
        else if (InputPattern == "Input3") {
            WillReturn.Add("2 2");
            WillReturn.Add("1000000000 1000000000");
            WillReturn.Add("200000000000000");
            WillReturn.Add("1");
            //2
            //0
        }
        else {
            string wkStr;
            while ((wkStr = Console.ReadLine()) != null) WillReturn.Add(wkStr);
        }
        return WillReturn;
    }

    static long[] mRunSumArr;

    static void Main()
    {
        List<string> InputList = GetInputList();
        long[] RArr = InputList[1].Split(' ').Select(pX => long.Parse(pX)).ToArray();
        Array.Sort(RArr);

        mRunSumArr = (long[])RArr.Clone();
        for (long I = 1; I <= mRunSumArr.GetUpperBound(0); I++) {
            mRunSumArr[I] += mRunSumArr[I - 1];
        }

        foreach (string EachStr in InputList.Skip(2)) {
            long X = long.Parse(EachStr);
            int ResultInd = ExecNibunhou_LowerOrEqual_Max(X, mRunSumArr);
            if (ResultInd == -1) {
                Console.WriteLine(0);
            }
            else {
                Console.WriteLine(ResultInd + 1);
            }
        }
    }

    // 二分法で、Val以下で最大の値を持つ、添字を返す
    static int ExecNibunhou_LowerOrEqual_Max(long pVal, long[] pArr)
    {
        // 最後の要素がVal以下の特殊ケース
        if (pVal >= pArr.Last()) {
            return pArr.GetUpperBound(0);
        }
        // 最初の要素がVal超えの特殊ケース
        if (pVal < pArr[0]) {
            return -1;
        }

        int L = 0;
        int R = pArr.GetUpperBound(0);

        while (L + 1 < R) {
            int Mid = (L + R) / 2;

            if (pArr[Mid] <= pVal) {
                L = Mid;
            }
            else {
                R = Mid;
            }
        }
        return L;
    }
}

解説

累積和を求めておいて、二分探索してます。