#include <bits/stdc++.h>

//************************************************
// HackerRank Prepare > Algorithms > Search: Pairs
//************************************************

// Given an array of integers and a target value, determine the number
// of pairs of array elements that have a difference equal to the
// target value.

using namespace std;

int pairs(int k, vector<int> arr) {
    sort(arr.begin(), arr.end());

    int count = 0;    
    size_t i = 0, j = 1;
    
    while (j < arr.size())
    {
        if (arr[j] - arr[i] == k)
        {
            count++;
            j++;
        }
        else if (arr[j] - arr[i] < k)
        {
            j++;            
        }
        else if (arr[j] - arr[i] > k)
        {
            i++;            
        }
    }

    return count;
}

int main()
{
    vector<tuple<int,vector<int>,int>> v = {
        // k  arr             expected 
        {  2, {1,5,3,4,2},    3 },
        {  1, {363374326,364147530,61825163,1073065718,1281246024,1399469912,428047635,491595254,879792181,1069262793},
                              0 },
        {  2, {1,3,5,8,6,4,2},5 },
    };
        

    for (auto i: v)
    {
        int k = get<0>(i);
        vector<int>& arr = get<1>(i);
        int expected = get<2>(i);
        
        int result = pairs(k, arr);
        cout << result << endl;
        cout << expected << endl;
        cout << "--------------\n";
    }
    

    return 0;
}