C++14 Minesweeper Console Game

minesweeper.cpp

#include <iostream>
#include <unordered_set>
#include <ctime>
#include <vector>

constexpr int n = 10;
int dx[8] = {-1, 0, 1, -1, 1, -1, 0, 1};
int dy[8] = {1, 1, 1, 0, 0, -1, -1, -1};
bool gameOver = false;

void printBoard(char(&board)[n][n], int mines) {
  std::cout << "Mines: " << mines << '\n';
  for (int i = 0; i < n; i++) {
    std::cout << "|";
    for (int j = 0; j < n; j++) {
      std::cout << " ";
      if (gameOver && board[i][j] == '*') {
        std::cout << '*';
      } else {
        std::cout << (board[i][j] == '*' ? '#' : board[i][j]);
      }
      std::cout << " |";
    }
    std::cout << '\n';
  }
}

std::string trim_all(std::string const& str, std::string nope) {
  std::unordered_set<char> us(nope.begin(), nope.end());
  std::string temp;
  for (int i = 0; i < str.size(); i++) {
    if (us.find(str[i]) == us.end())
      temp += str[i];
  }
  return temp;
}

bool valid_neighbor(int i, int j) {
  return 0 <= i && i < n && 0 <= j && j < n;
}

auto& input(int& y, int& x) {
  std::cout << "Enter a square (i, j) or q to quit: ";
  std::string line;

  if (!std::getline(std::cin >> std::ws, line)) {
    std::cout << "Invalid input. Exiting program.\n";
    std::cin.setstate(std::ios_base::failbit);
    return std::cin;
  }

  line = trim_all(line, " -()");
  if (line == "q") {
    gameOver = true;
    return std::cin;
  }

  if (line.find_first_of(",") == std::string::npos) {
    std::cout << "Invalid input. Exiting program.\n";
    std::cin.setstate(std::ios_base::failbit);
    return std::cin;
  }

  std::size_t pos = line.find_first_of(",");
  y = std::stoi(line.substr(0, pos));
  x = std::stoi(line.substr(pos + 1));

  if (!(0 <= y && y < n && 0 <= x && x < n)) {
    std::cout << "Out of range. Exiting program.\n";
    std::cin.setstate(std::ios_base::failbit);
  }
  return std::cin;
}

char dfs(char(&board)[n][n], bool(&visited)[n][n], int y, int x) {
  // Invariant: board[y][x] != '*' and y,x in [0,n-1]
  visited[y][x] = true;
  int count = 0;
  std::vector<std::pair<int, int>> neighbors;
  for (int i = 0; i < 8; i++) {
    if (!valid_neighbor(y + dy[i], x + dx[i]) || visited[y + dy[i]][x + dx[i]])
      continue;
    if (board[y + dy[i]][x + dx[i]] == '*')
      count++;
    else
      neighbors.push_back({y + dy[i], x + dx[i]});
  }
  if (count == 0) {
    for (auto p : neighbors) {
      board[p.first][p.second] = dfs(board, visited, p.first, p.second);
    }
    return '-';
  }
  return count + '0';
}

char dfs(char(&board)[n][n], int y, int x) {
  bool visited[n][n] = {};
  return dfs(board, visited, y, x);
}

int main() {
  std::srand(std::time(0));

  char board[n][n] = {};
  int mines = 10;

  for (int i = 0; i < n; i++) {
    for (int j = 0; j < n; j++) {
      board[i][j] = '#';
    }
  }

  for (int i = 0; i < mines;) {
    int y = rand() % n, x = rand() % n;
    if (board[y][x] != '*') {
      board[y][x] = '*';
      i++;
    }
  }

  printBoard(board, mines);

  int selections = 0;
  int y, x;
  while (input(y, x)) {
    if (gameOver) {
      printBoard(board, mines);
      break;
    }
    int idx = y * n + x;
    if (board[y][x] == '*') {
      gameOver = true;
    } else {
      board[y][x] = dfs(board, y, x);
    }

    printBoard(board, mines);
    selections++;

    if (selections == n*n - mines || gameOver) {
      if (selections == n - mines)
        std::cout << "You win.\n";
      else
        std::cout << "You lose.\n";
      break;
    }
  }
}