DivisibleSumPairs.cpp

#include <bits/stdc++.h>

using namespace std;

vector <string> split_string(string);

// Complete the divisibleSumPairs function below.
int divisibleSumPairs(int n, int k, vector<int> ar)
{
    auto howMany = 0;
    for (auto i = 0; i < n - 1; ++i)
    {
        for (auto j = i + 1; j < n; ++j)
        {
            if ((ar[i] + ar[j]) % k == 0)
            {
                ++howMany;
            }
        }
    }

    return howMany;
}

int main()
{
    ofstream fout(getenv("OUTPUT_PATH"));

    string nk_temp;
    getline(cin, nk_temp);

    vector <string> nk = split_string(nk_temp);

    int n = stoi(nk[0]);

    int k = stoi(nk[1]);

    string ar_temp_temp;
    getline(cin, ar_temp_temp);

    vector <string> ar_temp = split_string(ar_temp_temp);

    vector<int> ar(n);

    for (int i = 0; i < n; i++)
    {
        int ar_item = stoi(ar_temp[i]);

        ar[i] = ar_item;
    }

    int result = divisibleSumPairs(n, k, ar);

    fout << result << "\n";

    fout.close();

    return 0;
}

vector <string> split_string(string input_string)
{
    string::iterator new_end = unique(input_string.begin(), input_string.end(), [](const char &x, const char &y)
    {
        return x == y and x == ' ';
    });

    input_string.erase(new_end, input_string.end());

    while (input_string[input_string.length() - 1] == ' ')
    {
        input_string.pop_back();
    }

    vector <string> splits;
    char delimiter = ' ';

    size_t i = 0;
    size_t pos = input_string.find(delimiter);

    while (pos != string::npos)
    {
        splits.push_back(input_string.substr(i, pos - i));

        i = pos + 1;
        pos = input_string.find(delimiter, i);
    }

    splits.push_back(input_string.substr(i, min(pos, input_string.length()) - i + 1));

    return splits;
}