Diverse Arrays

    1#include <bits/stdc++.h>
    2using namespace std;
    3using ll = long long;
    4const int inf = 1e9;
    5const long long INF = 1e17; //❄️
    6int main() {
    7    ios::sync_with_stdio(0); cin.tie(0); 
    8    int n, k; cin >> n >> k;
    9    vector<int> a(n);
    10    for (int i = 0; i < n; i++) cin >> a[i];
    11    vector<int> f(n + 1);
    12    int cnt = 0;
    13    ll ans = 0;
    14    for (int l = 0, r = 0; l < n; l++) {
    15        while (r < n && cnt < k) {
    16            if (f[a[r]]++ == 0) cnt++;
    17            r++;
    18        } 
    19        if (cnt == k) ans += n - r + 1;
    20        if (--f[a[l]] == 0) cnt--;
    21    }
    22    cout << ans << '\n';
    23    return 0;
    24}