Submission #3590277

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Source Code Expand

using System;
using System.Linq;//リストの使用
using System.Collections.Generic;
using System.Text;//テキストの高速出力に必要
class Program
{
	static void Main()
	{
    string[] input = Console.ReadLine().Split(' ');//Splitで区切り文字を指定して複数個受け取る。
    long n = long.Parse(input[0]);
    long d = long.Parse(input[1]);
    long x = long.Parse(input[2]);
    float answer = 0;

    for(int i = 0; i < n; i++)
    {
      answer += (2*x + (4*i+1)*d)/4;//両方向の初項
      answer += ProgressionTwo(0.5f, i)*(-2*d)/4;//左方向の中間項
      answer += ProgressionOne(0.5f, i)*(2*x + 4*i*d - d)/4;
      answer += ProgressionZero(0.5f, i)*(x + 2*i*d)/4;
      answer += ProgressionTwo(0.5f, n-1-i)*(2*d)/4;//右方向の中間項
      answer += ProgressionOne(0.5f, n-1-i)*(2*x + 4*i*d + 3*d)/4;
      answer += ProgressionZero(0.5f, n-1-i)*(x + d + 2*i*d)/4;
      answer += (2*i+1) * (x+i*d) / (4*DivideMod(2,i));//左の最終項
      answer += (2*n-2*i-1) * (x+i*d+n*d) / (4*DivideMod(2,n-1-i));//右の最終項
    }
    //Console.WriteLine(ProgressionZero(n,d));
    //Console.WriteLine(ProgressionOne(n,d));
    //Console.WriteLine(ProgressionTwo(n,d));
		Console.WriteLine(answer);
	}

  static float ProgressionZero(float ratio, long n)
  {//等比数列の和　Σ(i=1~n)ratio^i = ratio + ratio^2 + ... + ratio^n
    if(n == 0) return 0;//項数が0の時
    if(ratio == 1) return n;//公比が1の時
    float product = DivideMod(ratio, n);//公比の項数乗
    float answer = ratio * (1-product) / (1-ratio);
    return answer;
  }

  static float ProgressionOne(float ratio, long n)
  {//等差×等比数列の和　Σ(i=1~n)i*ratio^i = 1*ratio + 2+ratio^2 + ... + n*ratio^n
    if(n == 0) return 0;//項数が0の時
    if(ratio == 1) return n*(n+1)/2;//公比が1の時
    float product = DivideMod(ratio, n);//公比の項数乗
    float answer = ratio * (1-product) / (1-ratio);
    answer -= n*product*ratio;
    answer /= 1-ratio;
    return answer;
  }

  static float ProgressionTwo(float ratio, long n)
  {//(等差)^2×等比数列の和　Σ(i=1~n)i^2*ratio^i = 1^2*ratio + 2^2+ratio^2 + ... + n^2*ratio^n
    if(n == 0) return 0;//項数が0の時
    if(ratio == 1) return n*(n+1)*(2*n+1)/6;//公比が1の時
    float product = DivideMod(ratio, n);//公比の項数乗
    float answer = 2 * ratio * (1-product) / (1-ratio);
    answer -= ratio;
    answer -= n*n*ratio*product;
    answer += n*n*ratio*ratio*product;
    answer -= (2*n-1)*ratio*product;
    answer /= ratio*ratio - 2*ratio + 1;
    return answer;
  }

  static float DivideMod(float x, long a)//戻り値はx^a、ただしaは整数。
  {
    long num = 2;
    float answer = 1;
    long check = a;
    float memo = x;
    
    while(check > 0)
    {
      if(check % num == num / 2)
      {
        check -= num / 2;
        answer *= memo;
      }
    memo *= memo;
    num *= 2;
    }
    return answer;
  }
  
}

Submission Info

Judge Result