https://cses.fi/paste/35d45c2a32ca0fd42babf7/
#include<bits/stdc++.h> #define ll long long using namespace std; int main(){ ll n,k; cin >> n >> k; vector < ll > v(n); for(ll i=0; i<n ; i++) cin >> v[i]; map<ll ,ll> prevSum; int currSum = 0 , res = 0; for(ll i=0; i<n ; ++i) { currSum += v[i]; if(currSum == k) res++; if(prevSum.count(currSum - k)) { res += prevSum[currSum - k]; } prevSum[currSum]++; } cout << res << '\n'; return 0; }