ABCDEF

Problem Link

#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;


int main(){

int arr[105];
int n, a, b, c, d, e, f, g;

vector<long> lhs; // lhs stores result of a * b + c
vector<long> rhs; // rhs stores result of d * (e + f)

cin >> n;
for(int i = 0; i < n; i++){
cin >> arr[i];
}

for(int i = 0; i < n; i++){
for(int j = 0; j < n; j++){
for(int k = 0; k < n; k++){

a = arr[i];
b = arr[j];
c = arr[k];

d = arr[i];
e = arr[j];
f = arr[k];

lhs.push_back((a * b) + c);

if(d != 0){
rhs.push_back(d * (e + f));
}
}
}
}


sort(lhs.begin(), lhs.end());
sort(rhs.begin(), rhs.end());

vector<long>::iterator it, l1, l2, u1, u2;

it = lhs.begin();

long result = 0;
while(it != lhs.end()){

l1 = lower_bound(lhs.begin(), lhs.end(), *it);
u1 = upper_bound(lhs.begin(), lhs.end(), *it);

l2 = lower_bound(rhs.begin(), rhs.end(), *it);
u2 = upper_bound(rhs.begin(), rhs.end(), *it);


result += (u1 - l1) * (u2 - l2);

it = u1;

}

cout << result << endl;

return 0;
}