Maximum sum

#include <iostream>
#include <vector>
#include <string>
#include <algorithm>
#include <map>
#include <set>
#include <queue>
#include <cmath>

using namespace std;

using ll  = long long;
using vi  = vector<int>;
using vll = vector<long long>;
using vs  = vector<string>;
using pii = pair<int, int>;

#define all(x) (x).begin(), (x).end()
#define pb push_back
#define sz(x) ((int)(x).size())
#define forn(i, n) for (int i = 0; i < (n); ++i)

using namespace std;

int main(){
  int n;
  cin >> n;
  vll v(n);
  forn(i, n) cin >> v[i];

  ll sum = v[0];
  ll maximum_sum = sum;

  for(int i = 1; i < n; i++){
    sum = max(v[i], v[i]+sum);
    maximum_sum = max(maximum_sum, sum);
  }

  cout << maximum_sum << endl;
}

Test 1

Verdict: ACCEPTED

Test 2

Verdict: ACCEPTED

Test 3

Verdict: ACCEPTED

Test 4

Verdict: ACCEPTED

Test 5

Verdict: ACCEPTED

Test 6

Verdict: ACCEPTED

Test 7

Verdict: ACCEPTED

Test 8

Verdict: ACCEPTED

Test 9

Verdict: ACCEPTED

Test 10

Verdict: ACCEPTED

Test 11

Verdict: ACCEPTED

Test 12

Verdict: ACCEPTED

Test 13

Verdict: ACCEPTED

Test 14

Verdict: ACCEPTED

Test 15

Verdict: ACCEPTED