CSES – Subarray Distinct Values

#include<bits/stdc++.h>
#define int long long
#define pii pair<int,int>
#define f first
#define s second
#define fastio ios_base::sync_with_stdio(0);cin.tie(0)
using namespace std;
//declare
int n,k;
vector<int> v;
map<int,int> cnt;
//
signed main(){
    fastio;
    cin>>n>>k;
    for(int i=0;i<n;i++){
        int x; cin>>x;
        v.push_back(x);
    }
    int L = 0, R = 0, now = 0, ans = 0;
    while(R < n){
        if(now <= k){
            ans += (R-L);
            if(cnt[v[R++]]++ == 0) now++;
        }
        else{
            if(--cnt[v[L++]] == 0) now--;
        }
    }
    while(L < R){
        if(now <= k) ans++;
        if(--cnt[v[L++]] == 0) now--;
    }
    cout<<ans<<"\n";
    return 0;
}