Submission #2124037

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Source Code Expand

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ABC084D {
    class Program {
        static void Main(string[] args) {
            bool[] primes = Enumerable.Repeat(true, 100001).ToArray();
            primes[0] = false;
            primes[1] = false;
            for (int i = 2; i < 100001; i++) {
                if (primes[i]) {
                    int num = i * 2;
                    while (num < 100001) {
                        primes[num] = false;
                        num += i;
                    }
                }
            }
            int[] like2017Nums = new int[100001];
            int likeNum = 0;
            for (int i = 0; i < 100001; i++) {
                if (primes[i] && primes[(i + 1) / 2]) {
                    likeNum++; //2は外れるので大丈夫
                }
                like2017Nums[i] = likeNum;
            }
            int Q = int.Parse(Console.ReadLine());
            for (int i = 0; i < Q; i++) {
                int[] input = Console.ReadLine().Split(' ').Select(s => int.Parse(s)).ToArray();
                int l = input[0];
                int r = input[1];
                Console.WriteLine(like2017Nums[r] - like2017Nums[l - 1]);
            }
        }
    }
}

Submission Info

Judge Result