08.cpp

#include <chrono>
#include <iostream>

void shift_row(char grid[6][50], int r, int n) {
  char copy[50];
  for (unsigned long c = 0; c < 50; c++) {
    copy[c] = grid[r][c];
  }

  for (int c = 0; c < 50; c++) {
    int src = c - n;
    if (src < 0) {
      src += 50;
    }
    grid[r][c] = copy[src];
  }
}

void shift_column(char grid[6][50], int c, int n) {
  char copy[6];
  for (int r = 0; r < 6; r++) {
    copy[r] = grid[r][c];
  }

  for (int r = 0; r < 6; r++) {
    int src = r - n;
    if (src < 0) {
      src += 6;
    }
    grid[r][c] = copy[src];
  }
}

int main() {
  auto tstart = std::chrono::high_resolution_clock::now();
  int pt1 = 0;

  std::string line;
  char grid[6][50] = {{0}};
  for (unsigned int r = 0; r < 6; r++) {
    for (unsigned int c = 0; c < 50; c++) {
      grid[r][c] = 0;
    }
  }

  while (std::getline(std::cin, line)) {
    if (line.compare(0, 4, "rect") == 0) {
      unsigned int i = 5;
      int width = std::stoi(&line[i]);
      while (line[i - 1] != 'x') {
        i++;
      }
      int height = std::stoi(&line[i]);
      for (int r = 0; r < height; r++) {
        for (int c = 0; c < width; c++) {
          grid[r][c] = 1;
        }
      }
    } else {
      char orientation = line[7];
      unsigned int i = 7;
      while (line[i] < '0' || line[i] > '9') {
        i++;
      }
      int src = std::stoi(&line[i]);
      i += 4;
      while (line[i] < '0' || line[i] > '9') {
        i++;
      }
      int amount = std::stoi(&line[i]);

      if (orientation == 'c') {
        shift_column(grid, src, amount);
      } else {
        shift_row(grid, src, amount);
      }
    }
  }

  for (unsigned int r = 0; r < 6; r++) {
    for (unsigned int c = 0; c < 50; c++) {
      pt1 += grid[r][c];
    }
  }

  std::cout << "--- Day 8: Two-Factor Authentication ---\n";
  std::cout << "Part 1: " << pt1 << "\n";
  std::cout << "Part 2:\n";
  for (int r = 0; r < 6; r++) {
    for (int c = 0; c < 50; c++) {
      pt1 += grid[r][c];
      std::cout << (grid[r][c] ? '#' : ' ');
    }
    std::cout << "\n";
  }

  auto tstop = std::chrono::high_resolution_clock::now();
  auto duration =
      std::chrono::duration_cast<std::chrono::microseconds>(tstop - tstart);
  std::cout << "Time: " << duration.count() << " μs"
            << "\n";
  return EXIT_SUCCESS;
}