2018-9.cpp

#include <iostream>
#include <list>
#include <vector>

long highest(const std::vector<long> &s) {
  long i = 0;
  for (auto j : s) {
    if (j > i) {
      i = j;
    }
  }
  return i;
}

void print_marbles(const std::list<int> &m)  {
  for (auto i : m) {
    std::cout << i << " ";
  }
  std::cout << '\n';;
}

int main() {
  int players = 430;
  int last = 7158800;

  // zero init score vector
  std::vector<long> scores(players, 0);

  // init marbles, linked list
  std::list<int> marbles = {0};

  // the next to insert, the head iterator
  int i = 1;
  auto h = marbles.begin();
  while (true) {
    // debug print too
    if (i % 71588 == 0) {
      std::cout << "current i " << i << " highest score " << highest(scores)
                << std::endl;
    }

    auto score = (i % 23) == 0;

    if (score) {
      auto pi = i % players; // player index
      auto ps = scores[pi];  // previous score

      // find anti-closewise by 7, remove that value
      for (int ir = 0; ir < 7; ir++) {
        if (h == marbles.begin()) {
          h = marbles.end();
          h--; // one pass end so --
        } else {
          h--;
        }
      }
      auto v = *h;
      scores[pi] = ps + i + v;
      // Iterator following the last removed element.
      // If pos refers to the last element, then the end() iterator is returned.
      h = marbles.erase(h);
      if (h == marbles.end()) {
        h = marbles.begin();
      }
    } else {
      for (int ia = 0; ia < 2; ia++) {
        if (h == marbles.end()){
          h = marbles.begin();
          h++; // insert before pos
        }else {
          h++;
        }
      }
      h = marbles.insert(h, i); // return inserted pos
    }
    // print_marbles(marbles);
    if (i > last) {
      break;
    }
    i++;
    continue;
  }

  // print_marbles(marbles);
  std::cout << "current i " << i << " highest score " << highest(scores)
            << std::endl;
  return 0;
}