TruckTour.cpp

#include <bits/stdc++.h>

using namespace std;

string ltrim(const string &);
string rtrim(const string &);
vector<string> split(const string &);

/*
 * Complete the 'truckTour' function below.
 *
 * The function is expected to return an INTEGER.
 * The function accepts 2D_INTEGER_ARRAY petrolpumps as parameter.
 */

int truckTour(vector<vector<int>> petrolpumps) {
  const int N = petrolpumps.size();
  vector<int> fuel_diff(N, 0);

  for (int i = 0; i < N; i++) {
    fuel_diff[i] = petrolpumps[i][0] - petrolpumps[i][1];
  }

  for (int i = 0; i < N; i++) {
    if (fuel_diff[i] < 0) {
      continue;
    }

    int sum = 0;
    int j = 0;
    for (; j < N; j++) {
      sum += fuel_diff[(i + j) % N];
      if (sum < 0) break;
    }

    if (j == N) {
      return i;
    }
  }

  return -1;
}

int main() {
  ofstream fout(getenv("OUTPUT_PATH"));

  string n_temp;
  getline(cin, n_temp);

  int n = stoi(ltrim(rtrim(n_temp)));

  vector<vector<int>> petrolpumps(n);

  for (int i = 0; i < n; i++) {
    petrolpumps[i].resize(2);

    string petrolpumps_row_temp_temp;
    getline(cin, petrolpumps_row_temp_temp);

    vector<string> petrolpumps_row_temp =
        split(rtrim(petrolpumps_row_temp_temp));

    for (int j = 0; j < 2; j++) {
      int petrolpumps_row_item = stoi(petrolpumps_row_temp[j]);

      petrolpumps[i][j] = petrolpumps_row_item;
    }
  }

  int result = truckTour(petrolpumps);

  fout << result << "\n";

  fout.close();

  return 0;
}

string ltrim(const string &str) {
  string s(str);

  s.erase(s.begin(),
          find_if(s.begin(), s.end(), not1(ptr_fun<int, int>(isspace))));

  return s;
}

string rtrim(const string &str) {
  string s(str);

  s.erase(
      find_if(s.rbegin(), s.rend(), not1(ptr_fun<int, int>(isspace))).base(),
      s.end());

  return s;
}

vector<string> split(const string &str) {
  vector<string> tokens;

  string::size_type start = 0;
  string::size_type end = 0;

  while ((end = str.find(" ", start)) != string::npos) {
    tokens.push_back(str.substr(start, end - start));

    start = end + 1;
  }

  tokens.push_back(str.substr(start));

  return tokens;
}