Algorithms/Amicable Number at master · codeingwolf/Algorithms · GitHub

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// amicable pairs in an array.
#include <bits/stdc++.h>
using namespace std;

int sumOfDiv(int x)
{
    // 1 is a proper divisor
    int sum = 1;
    for (int i = 2; i <= sqrt(x); i++)
    {
        if (x % i == 0)
        {
            sum += i;

            if (x / i != i)
                sum += x / i;
        }
    }
    return sum;
}

bool isAmicable(int a, int b)
{
    return (sumOfDiv(a) == b &&
            sumOfDiv(b) == a);
}

int countPairs(int arr[], int n)
{
    int count = 0;


    for (int i = 0; i < n; i++)
        for (int j = i + 1; j < n; j++)
            if (isAmicable(arr[i], arr[j]))
                count++;

    return count;
}

int main()
{
    int arr1[] = { 220, 284, 1184,
                   1210, 2, 5 };
    int n1 = sizeof(arr1) / sizeof(arr1[0]);
    cout << countPairs(arr1, n1)
         << endl;

    int arr2[] = { 2620, 2924, 5020,
                   5564, 6232, 6368 };
    int n2 = sizeof(arr2) / sizeof(arr2[0]);
    cout << countPairs(arr2, n2);
    return 0;
}