aoc24/08/main.cc

#include <fstream>
#include <iostream>
#include <sstream>
#include <vector>
#include <set>

using namespace std;

vector<vector<char>> parseGrid(const char *path) {
  vector<vector<char>> grid;
  ifstream input(path);
  string line;
  char c;

  while (getline(input, line)) {
    stringstream line_stream;
    line_stream << line;
    vector<char> row;
    while (line_stream >> c) {
      row.push_back(c);
    }
    grid.push_back(row);
  }
  return grid;
}

void printGrid(vector<vector<char>> grid) {
  for (int y = 0; y < grid.size(); y++) {
    for (int x = 0; x < grid[y].size(); x++) {
      cout << grid[y][x];
    }
    cout << endl;
  }
}

void printAntinodes(vector<vector<char>> grid, vector<vector<bool>> antinodes) {
  for (int y = 0; y < antinodes.size(); y++) {
    for (int x = 0; x < antinodes[y].size(); x++) {
      if (antinodes[y][x]) {
        cout << '#';
      } else {
        cout << grid[y][x];
      }
    }
    cout << endl;
  }
}

int countAntinodes(vector<vector<char>> grid, vector<vector<bool>> &antinodes, int y1, int x1, char c) {
  int sum = 0;
  for (int y2 = 0; y2 < grid.size(); y2++) {
    for (int x2 = 0; x2 < grid[y2].size(); x2++) {
      if (grid[y2][x2] == c && y1 != y2 && x1 != x2) {
        // distance vector
        int x_delta = x1 - x2;
        int y_delta = y1 - y2;

        // first antinode
        int x3 = x1 + x_delta;
        int y3 = y1 + y_delta;
        if (x3 >= 0 && x3 < grid[0].size() && y3 >= 0 && y3 < grid.size() && !antinodes[y3][x3]) {
          antinodes[y3][x3] = true;
          sum++;
        }

        // second antinode
        x3 = x2 - x_delta;
        y3 = y2 - y_delta;
        if (x3 >= 0 && x3 < grid[0].size() && y3 >= 0 && y3 < grid.size() && !antinodes[y3][x3]) {
          antinodes[y3][x3] = true;
          sum++;
        } 
      }
    }
  }
  // cout << "Antinodes after " << c << ":" << endl;
  // printAntinodes(grid, antinodes);
  
  return sum;
}

int countAntinodesAdjusted(vector<vector<char>> grid, vector<vector<bool>> &antinodes, int y1, int x1, char c) {
  int sum = 0;
  for (int y2 = 0; y2 < grid.size(); y2++) {
    for (int x2 = 0; x2 < grid[y2].size(); x2++) {
      if (grid[y2][x2] == c && y1 != y2 && x1 != x2) {
        // distance vector
        int x_delta = x1 - x2;
        int y_delta = y1 - y2;

        int x3 = x1;
        int y3 = y1;

        while (x3 >= 0 && x3 < grid[0].size() && y3 >= 0 && y3 < grid.size()) {
          if(!antinodes[y3][x3]) {
            sum++;
            antinodes[y3][x3] = true;
          }
          x3 += x_delta;
          y3 += y_delta;
        }

        x3 = x2;
        y3 = y2;

        while (x3 >= 0 && x3 < grid[0].size() && y3 >= 0 && y3 < grid.size()) {
          if(!antinodes[y3][x3]) {
            sum++;
            antinodes[y3][x3] = true;
          }
          x3 -= x_delta;
          y3 -= y_delta;
        }
      }
    }
  }
  // cout << "Antinodes after " << c << ":" << endl;
  // printAntinodes(grid, antinodes);
  
  return sum;
}

int part1(const char *path) {
  vector<vector<char>> grid = parseGrid(path);
  vector<vector<bool>> antinodes;
  // initialize antinodes grid
  for (int y = 0; y < grid.size(); y++) {
    vector<bool> row;
    for (int x = 0; x < grid[y].size(); x++) {
      row.push_back(false);
    }
    antinodes.push_back(row);
  }

  set<char, greater<char>> visited;

  int sum = 0;
  for (int y = 0; y < grid.size(); y++) {
    for (int x = 0; x < grid[y].size(); x++) {
      if (grid[y][x] != '.' && visited.count(grid[y][x]) == 0) {
        sum += countAntinodes(grid, antinodes, y, x, grid[y][x]);
      }
    }
  }

  return sum;
}

int part2(const char *path) {
  vector<vector<char>> grid = parseGrid(path);
  vector<vector<bool>> antinodes;
  // initialize antinodes grid
  for (int y = 0; y < grid.size(); y++) {
    vector<bool> row;
    for (int x = 0; x < grid[y].size(); x++) {
      row.push_back(false);
    }
    antinodes.push_back(row);
  }

  set<char, greater<char>> visited;

  int sum = 0;
  for (int y = 0; y < grid.size(); y++) {
    for (int x = 0; x < grid[y].size(); x++) {
      if (grid[y][x] != '.' && visited.count(grid[y][x]) == 0) {
        sum += countAntinodesAdjusted(grid, antinodes, y, x, grid[y][x]);
      }
    }
  }

  return sum;
}

int main(int argc, char *argv[]) {
  cout << "example1: " << part1("example") << endl;
  cout << "input1: " << part1("input") << endl;
  cout << "example2: " << part2("example") << endl;
  cout << "input2: " << part2("input") << endl;
  return 0;
}