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  1. using System;
  2.  
  3. namespace PerfectNumbers
  4. {
  5.     class Program
  6.     {
  7.         static int CalcSumOfDivisors(int n)
  8.         {
  9.             int sum = 0;
  10.             for (int i = 1; i < n; i++)
  11.             {
  12.                 if (n % i == 0)
  13.                 {
  14.                     sum += i;
  15.                 }
  16.             }
  17.             return sum;
  18.         }
  19.  
  20.         static void PrintAllPerfectNumbers(int n)
  21.         {
  22.             for (int c = 2; c <= n; c++)
  23.             {
  24.                 if (CalcSumOfDivisors(c) == c)
  25.                 {
  26.                     Console.WriteLine(c);
  27.                 }
  28.             }
  29.         }
  30.  
  31.         static void PrintAllAmicableNumbersPairs(int n)
  32.         {
  33.             for (int i = 2; i <= n; i++)
  34.             {
  35.                 int sumOfDivisorsI = CalcSumOfDivisors(i);
  36.                 if (CalcSumOfDivisors(sumOfDivisorsI) == i && sumOfDivisorsI != i && i < sumOfDivisorsI)
  37.                 {
  38.                     Console.WriteLine("({0}, {1})", i, sumOfDivisorsI);
  39.                 }  
  40.             }
  41.         }
  42.  
  43.         static void Main(string[] args)
  44.         {
  45.             Console.WriteLine("Enter a number n: ");
  46.             int inputNumber = int.Parse(Console.ReadLine());
  47.             Console.WriteLine("All perfect numbers in the range [2; {0}]:", inputNumber);
  48.             PrintAllPerfectNumbers(inputNumber);
  49.             Console.WriteLine("All friendly numbers in the range [2; {0}]:", inputNumber);
  50.             PrintAllAmicableNumbersPairs(inputNumber);
  51.         }
  52.     }
  53. }
  54.  
Success #stdin #stdout 0.64s 24492KB
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stdin
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10000
stdout
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Enter a number n: 
All perfect numbers in the range [2; 10000]:
6
28
496
8128
All friendly numbers in the range [2; 10000]:
(220, 284)
(1184, 1210)
(2620, 2924)
(5020, 5564)
(6232, 6368)
https://ideone.com/5nBqH3
language:
C# (gmcs 5.20.1)
created:
1 year ago
visibility:
public

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