Codeforces Round #153 (Div. 1) 252C(Div 2) Or 251A. Points on Line Solution

  Problem Link:  https://codeforces.com/problemset/problem/251/A

Solution in C++:

1. /// La ilaha illellahu muhammadur rasulullah
2. ///******Bismillahir-Rahmanir-Rahim******///
3. /// Abul Hasnat Tonmoy
4. /// Department of CSE,23rd batch
5. /// Islamic University,Bangladesh
6. ///**********ALLAH IS ALMIGHTY************///
7. #include <bits/stdc++.h>
8. using namespace std;
9. #define ll long long int
10. int main() {
11. ios_base::sync_with_stdio(0);
12. cin.tie(0);
13. ll n, k, i, index, sum = 0, r;
14. cin >> n >> k;
15. std::vector<int> v(n);
16. for (int i = 0; i < n; i++) cin >> v[i];
17. for (int i = 0; i < n; i++) {
18. index = upper_bound(v.begin(), v.end(), v[i] + k) - v.begin();
19. r = index - 1 - i;
20. sum += (r * (r - 1)) / 2;
21. }
22. cout << sum << endl;
23. }