CSES – Subarray Sums I

#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,x;
vector<int> v;
//
signed main(){
    fastio;
    cin>>n>>x;
    for(int i=0;i<n;i++){
        int x; cin>>x;
        v.push_back(x);
    }
    v.push_back(-1e18);
    int L = 0, R = 1, sum = v[0], ans = 0;
    while(R <= n){
        if(L == R){
            sum += v[R++];
            continue;
        }
        if(sum == x) ans++;
        if(sum >= x) sum -= v[L++];
        else sum += v[R++];
    }
    cout<<ans<<"\n";
    return 0;
}