AOC day 3 part 1

1.cpp

#include <bits/stdc++.h>
#include <fstream>
#include <string>

#define ll long long

using namespace std;

void solution() {
  string row;
  ll ans = 0;

  map<pair<int, int>, pair<int, int>> numbers;
  vector<pair<int, int>> symbols;
  vector<string> rows;

  ifstream input("input.txt");
  int row_number = 0;

  if (input.is_open()) {
    while (getline(input, row)) {
      rows.push_back(row);
    }
    input.close();
  }
  for (string row : rows) {
    // Get number positions
    int num_start = -1;
    int num_end = -1;
    string number = "";

    for (int col = 0; col < row.length(); ++col) {
      if (row[col] - '0' >= 0 && '9' - row[col] >= 0) {
        if (num_start == -1) {
          num_start = col;
          num_end = col;
        } else {
          num_end++;
        }
        number += row[col];
      } else {
        // Check if there was a num, add it.
        if (num_start != -1) {
          int number_int = (int)stoi(number);
          int i = num_start;
          while (i <= num_end) {
            numbers[{row_number, i}] = {num_start, num_end};
            i++;
          }
        }
        num_start = -1;
        num_end = -1;
        number = "";

        // Add symbol.
        if (row[col] != '.') {
          symbols.push_back({row_number, col});
        }
      }
    }
    if (num_start != -1) {
      int number_int = (int)stoi(number);
      int i = num_start;
      while (i <= num_end) {
        numbers[{row_number, i}] = {num_start, num_end};
        i++;
      }
    }

    row_number++;
  }

  set<tuple<int, int, int>> part_numbers;

  // Go through all symbols and check the 8 directions.
  for (auto s : symbols) {
    ll x = s.first;
    ll y = s.second;

    // W
    if (numbers.find({x, y - 1}) != numbers.end()) {
      pair<int, int> coords = numbers[{x, y - 1}];
      part_numbers.insert({x, coords.first, coords.second});
    }
    // SW
    if (numbers.find({x + 1, y - 1}) != numbers.end()) {
      pair<int, int> coords = numbers[{x + 1, y - 1}];
      part_numbers.insert({x + 1, coords.first, coords.second});
    }
    // S
    if (numbers.find({x + 1, y}) != numbers.end()) {
      pair<int, int> coords = numbers[{x + 1, y}];
      part_numbers.insert({x + 1, coords.first, coords.second});
    }
    // SE
    if (numbers.find({x + 1, y + 1}) != numbers.end()) {
      pair<int, int> coords = numbers[{x + 1, y + 1}];
      part_numbers.insert({x + 1, coords.first, coords.second});
    }
    // E
    if (numbers.find({x, y + 1}) != numbers.end()) {
      pair<int, int> coords = numbers[{x, y + 1}];
      part_numbers.insert({x, coords.first, coords.second});
    }
    // NE
    if (numbers.find({x - 1, y + 1}) != numbers.end()) {
      pair<int, int> coords = numbers[{x - 1, y + 1}];
      part_numbers.insert({x - 1, coords.first, coords.second});
    }
    // N
    if (numbers.find({x - 1, y}) != numbers.end()) {
      pair<int, int> coords = numbers[{x - 1, y}];
      part_numbers.insert({x - 1, coords.first, coords.second});
    }
    // NW
    if (numbers.find({x - 1, y - 1}) != numbers.end()) {
      pair<int, int> coords = numbers[{x - 1, y - 1}];
      part_numbers.insert({x - 1, coords.first, coords.second});
    }
  }

  for (auto coordinates : part_numbers) {
    string row = rows[get<0>(coordinates)];
    int start_number = get<1>(coordinates);
    int end_number = get<2>(coordinates);

    string number = "";
    while (start_number <= end_number) {
      number += row[start_number];
      start_number++;
    }
    ans += stoi(number);
  }

  printf("%lld\n", ans);
}

int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  int t = 1;

  while (t--)
    solution();

  return 0;
}