Problem p03850 (C++)

Buggy submission (status: Runtime Error):
#include <algorithm>
#include <bitset>
#include <cassert>
#include <cctype>
#include <cfloat>
#include <climits>
#include <cmath>
#include <complex>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctime>
#include <deque>
#include <fstream>
#include <functional>
#include <iomanip>
#include <iostream>
#include <iterator>
#include <list>
#include <map>
#include <memory>
#include <numeric>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <vector>

#if __cplusplus >= 201103L
#include <array>
#include <forward_list>
#include <initializer_list>
#include <tuple>

#define cauto const auto &
#else

#endif

using namespace std;

typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;

typedef vector<int> vint;
typedef vector<vector<int>> vvint;
typedef vector<long long> vll;
typedef vector<vector<long long>> vvll;

#define VV(T) vector<vector<T>>

template <class T>
void initvv(vector<vector<T>> &v, int a, int b, const T &t = T()) {
  v.assign(a, vector<T>(b, t));
}

template <class F, class T> void convert(const F &f, T &t) {
  stringstream ss;
  ss << f;
  ss >> t;
}

#define GET_MACRO(_1, _2, _3, NAME, ...) NAME
#define _rep(i, n) _rep2((i), 0, (n))
#define _rep2(i, a, b) for (int i = (a); i < (b); ++i)
#define rep(...) GET_MACRO(__VA_ARGS__, _rep2, _rep)(__VA_ARGS__)
#define ALL(v) (v).begin(), (v).end()
#define PB push_back
#define fi first
#define se second
#define mkp make_pair
#define DEBUG
#ifdef DEBUG
#define dump(x) cout << #x << " = " << (x) << endl;
#define debug(x)                                                               \
  cout << #x << " = " << (x) << " (L" << __LINE__ << ")"                       \
       << " " << __FILE__ << endl;
#else
#define dump(x)
#define debug(x)
#endif

#define MOD 1000000007LL
#define EPS 1e-8
#define INF 0x3f3f3f3f
#define INFL 0x3f3f3f3f3f3f3f3fLL
#define maxs(x, y) x = max(x, y)
#define mins(x, y) x = min(x, y)

ll mainmain() {
  int n;
  cin >> n;
  ll ans1;
  cin >> ans1;
  if (n == 1) {
    return ans1;
  }
  vint op(n - 1);
  vll v(n - 1);
  vint minus;
  rep(i, n - 1) {
    char t;
    cin >> t;
    cin >> v[i];
    if (t == '-') {
      minus.PB(i);
      op[i] = -1;
    } else {
      op[i] = 1;
    }
  }
  vll suf(n - 1);
  for (int i = n - 2; i >= 0; i--) {
    suf[i] = v[i];
    if (i < n - 2)
      suf[i] += suf[i + 1];
  }
  ll ans2 = -INFL;
  ll tval = ans1;
  int p = 0;
  rep(i, minus.size() - 1) {
    int l = minus[i];
    int r = minus[i + 1];
    while (p < l)
      tval += op[p] * v[p], p++;
    ll tmp = suf[l] - suf[r];
    tmp *= -1;
    // cout<<l<<" "<<r<<endl;
    // cout<<tval<<" "<<tmp<<" "<<suf[r]<<endl;
    tmp += tval;
    tmp += suf[r];
    maxs(ans2, tmp);
  }
  return ans2;
}

signed main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout << fixed << setprecision(20);
  cout << mainmain() << endl;
}

Fixed submission:
#include <algorithm>
#include <bitset>
#include <cassert>
#include <cctype>
#include <cfloat>
#include <climits>
#include <cmath>
#include <complex>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctime>
#include <deque>
#include <fstream>
#include <functional>
#include <iomanip>
#include <iostream>
#include <iterator>
#include <list>
#include <map>
#include <memory>
#include <numeric>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <vector>

#if __cplusplus >= 201103L
#include <array>
#include <forward_list>
#include <initializer_list>
#include <tuple>

#define cauto const auto &
#else

#endif

using namespace std;

typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;

typedef vector<int> vint;
typedef vector<vector<int>> vvint;
typedef vector<long long> vll;
typedef vector<vector<long long>> vvll;

#define VV(T) vector<vector<T>>

template <class T>
void initvv(vector<vector<T>> &v, int a, int b, const T &t = T()) {
  v.assign(a, vector<T>(b, t));
}

template <class F, class T> void convert(const F &f, T &t) {
  stringstream ss;
  ss << f;
  ss >> t;
}

#define GET_MACRO(_1, _2, _3, NAME, ...) NAME
#define _rep(i, n) _rep2((i), 0, (n))
#define _rep2(i, a, b) for (int i = (a); i < (b); ++i)
#define rep(...) GET_MACRO(__VA_ARGS__, _rep2, _rep)(__VA_ARGS__)
#define ALL(v) (v).begin(), (v).end()
#define PB push_back
#define fi first
#define se second
#define mkp make_pair
#define DEBUG
#ifdef DEBUG
#define dump(x) cout << #x << " = " << (x) << endl;
#define debug(x)                                                               \
  cout << #x << " = " << (x) << " (L" << __LINE__ << ")"                       \
       << " " << __FILE__ << endl;
#else
#define dump(x)
#define debug(x)
#endif

#define MOD 1000000007LL
#define EPS 1e-8
#define INF 0x3f3f3f3f
#define INFL 0x3f3f3f3f3f3f3f3fLL
#define maxs(x, y) x = max(x, y)
#define mins(x, y) x = min(x, y)

ll mainmain() {
  int n;
  cin >> n;
  ll ans1;
  cin >> ans1;
  if (n == 1) {
    return ans1;
  }
  vint op(n - 1);
  vll v(n - 1);
  vint minus;
  rep(i, n - 1) {
    char t;
    cin >> t;
    cin >> v[i];
    if (t == '-') {
      minus.PB(i);
      op[i] = -1;
    } else {
      op[i] = 1;
    }
  }
  vll suf(n - 1);
  for (int i = n - 2; i >= 0; i--) {
    suf[i] = v[i];
    if (i < n - 2)
      suf[i] += suf[i + 1];
  }
  ll ans2 = -INFL;
  ll tval = ans1;
  int p = 0;
  if (minus.size() > 1)
    rep(i, minus.size() - 1) {
      int l = minus[i];
      int r = minus[i + 1];
      while (p < l)
        tval += op[p] * v[p], p++;
      ll tmp = suf[l] - suf[r];
      tmp *= -1;
      // cout<<l<<" "<<r<<endl;
      // cout<<tval<<" "<<tmp<<" "<<suf[r]<<endl;
      tmp += tval;
      tmp += suf[r];
      maxs(ans2, tmp);
    }
  ll tmp = ans1;
  rep(i, n - 1) tmp += op[i] * v[i];
  maxs(ans2, tmp);
  return ans2;
}

signed main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout << fixed << setprecision(20);
  cout << mainmain() << endl;
}