// Solutions to the Advent Of Code 2024.
// Copyright (C) 2024  Stefan Müller
//
// This program is free software: you can redistribute it and/or modify it under
// the terms of the GNU General Public License as published by the Free Software
// Foundation, either version 3 of the License, or (at your option) any later
// version.
//
// This program is distributed in the hope that it will be useful, but WITHOUT
// ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
// FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License along with
// this program.  If not, see <http://www.gnu.org/licenses/>.

#include <iostream>

#include <aoc/HistorianHysteria.hpp>

std::string HistorianHysteria::getPuzzleName() const
{
    return "Day 1: Historian Hysteria";
}

std::string HistorianHysteria::getInputFileName() const
{
    return "historian_hysteria.txt";
}

void HistorianHysteria::processDataLine(const std::string& line)
{
    auto pos{ line.find("   ") };
    left_.insert(std::stoi(line.substr(0, pos)));
    right_.insert(std::stoi(line.substr(pos + 3)));
}

void HistorianHysteria::finish()
{
    int prev{ 0 };
    auto nSame{ 0 };
    auto leftIterator{ left_.begin() };
    auto rightIterator{ right_.begin() };
    auto rightSameIterator{ right_.begin() };

    while (leftIterator != left_.end())
    {
        part1 += abs(*leftIterator - *rightIterator);

        if (prev != *leftIterator)
        {
            nSame = 0;
            // Skips over numbers in the right list that are smaller than the current left number.
            while (rightSameIterator != right_.end() && *rightSameIterator < *leftIterator)
            {
                rightSameIterator++;
            }
            // Counts the occurrences of the current left number in the right list.
            while (rightSameIterator != right_.end() && *rightSameIterator == *leftIterator)
            {
                rightSameIterator++;
                nSame++;
            }
            prev = *leftIterator;
        }
        part2 += *leftIterator * nSame;

        leftIterator++;
        rightIterator++;
    }
}