Sanduiche - Neps

#include <bits/stdc++.h>

#define forn(l, r) for(int i = l; i < (r); ++i)
#define TAM 1000100
#define SYNC ios::sync_with_stdio(0);
#define $ << ' ' <<
#define F first
#define S second
#define endl << '\n'


using namespace std;

using ll = long long int;
using ii = pair<int, int>;
using vii = vector<ii>;
using vi = vector<int>;
using graph = vector<vi>;
const int INF = 0x3f3f3f3f;
const int MAXN = 112345;
const ll mod = 1000000007;

int sum[TAM], san[TAM];
int sufixsum[TAM];

int bin_search(int l, int r, int val) {
    int mid = 0;
    while (l <= r) {
        if (sum[(l+r)/2] >= val) {
            mid = (l+r)/2;
            r = mid-1;
        } else {
            l = (l+r)/2+1;
        }
    }
    return sum[mid] == val ? mid : -1;
}


int main() {
    SYNC
    int n, d, pairs = 0, soma=0;
    cin >> n >> d;
    forn (0, n) {
        cin >> san[i];
        soma += san[i];
        sum[i] = soma;
    }
    soma = 0;
    for (int i = n-1; i >= 0; --i) {
        soma += san[i];
        sufixsum[i] = soma;
    }


    forn (0, n) {
        if (!i) {
            if(bin_search(i, n-1, d)+1) {
                pairs++;
            }
        } else {
            if(bin_search(i, n-1, d+sum[i-1])+1) {
                pairs++;
            }
        }
    }
    for (int i = n-1; i > 0; --i) {
        if (bin_search(0, i-1, d-sufixsum[i])+1) {
                pairs++;
            }
    }
    cout << pairs endl;
}