Phước Thành Nguyễn

Your algorithm complexity is O(n^4), so the program runs very slow. Here is my solution in O(nlogn):

#include<bits/stdc++.h>
using namespace std;
int main(){
    vector<int> sumDivisors(100001,0);
    for(int i=1;i<=50000;i++)
        for(int j=i*2;j<=100000;j+=i) sumDivisors[j]+=i;
    for(int A=1;A<=100000;A++)
    {
        int sumDivisorsOfA = sumDivisors[A];
        int B = sumDivisorsOfA-1;
        if(B<A || B>100000) continue;
        int sumDivisorsOfB = sumDivisors[B];
        if (sumDivisorsOfB == A+1) {
            cout << A << " - " << B << endl;
        }
    }
    return 0;
}