--- Day 15: Rambunctious Recitation ---

#include <algorithm>
#include <iostream>
#include <iterator>
#include <fstream>
#include <sstream>
#include <string>
#include <vector>
#include <map>

void PrintAnswer(int turn, int num)
{
    std::cout << "Turn " << turn << " - Spoken: " << num << std::endl;
}

int main()
{
    std::string text;
    std::ifstream ifs;
    ifs.open("data.txt", std::ifstream::in);

    std::vector<int> order;
    while (getline(ifs, text, ','))
    {
        order.push_back(atoi(text.c_str()));
    }

    int num = 0;
    int turn = 0;
    int lastNum = -1;
    std::map<int, int> number;
    std::map<int, std::pair<int, int>> last;
    while (turn < 30000000)
    {
        num = 0;
        turn++;

        if (turn > order.size())
        {
            if (number[lastNum] > 1) //if spoken before, next number is difference between last turn and last time spoken.
            {
                num = last[lastNum].first - last[lastNum].second;
            }
            //if last number is new, next number spoken is 0
        }
        else //starting numbers
        {
            num = order[turn - 1];
        }

        number[num]++;
        std::swap(last[num].first, last[num].second);
        last[num].first = turn;
        lastNum = num;
    }

    PrintAnswer(turn, num);

    return 0;
}