Advent Of Code 2024 - Problem 1 Part 2

aoc-2024-1-2.cpp

#include <iostream>
#include <fstream>
#include <string>
#include <ctype.h>
#include <vector>
#include <algorithm>
#include <unordered_map>
#include <sstream>

using namespace std;

int main()
{
  ifstream infile("input.txt");

  if (!infile.is_open()) {
    cout << "File prob\n";
    return -1;
  }

  std::vector<int> firstList;
  std::unordered_map<int, size_t> nOccurences;
  string line;
  while (infile.good()) {
    getline(infile, line);

    if (line.empty()) continue;
    
    std::stringstream ss(line);
    int list1Location, list2Location;
    ss >> list1Location >> list2Location;
    
    firstList.push_back(list1Location);
    
    nOccurences[list2Location]++;
  }
  infile.close();

  long long totalSimilarity = 0;

  for (int n : firstList) {
    totalSimilarity += n * nOccurences[n];
  }

  std::cout << totalSimilarity << std::endl;
}