Input validation

[slidingtile] / sliding_tile_lib.cc

#include "sliding_tile_lib.h"

#include <istream>

signed char adjacent[BOARD_SIZE][5] = {
  1,   4,   -1,  -1,  -1,
  0,   2,   5,   -1,  -1,
  1,   3,   6,   -1,  -1,
  2,   7,   -1,  -1,  -1,
  0,   5,   8,   -1,  -1,
  1,   4,   6,   9,   -1,
  2,   5,   7,   10,  -1,
  3,   6,   11,  -1,  -1,
  4,   9,   12,  -1,  -1,
  5,   8,   10,  13,  -1,
  6,   9,   11,  14,  -1,
  7,   10,  15,  -1,  -1,
  8,   13,  -1,  -1,  -1,
  9,   12,  14,  -1,  -1,
  10,  13,  15,  -1,  -1,
  11,  14,  -1,  -1,  -1,
};

bool Board::is_valid() {
  bool seen[BOARD_SIZE];
  for (int i = 0; i < BOARD_SIZE; i++) {
    seen[i] = false;
  }

  for (int i = 0; i < BOARD_SIZE; i++) {
    if (board[i] < 0 || board[i] >= BOARD_SIZE || seen[board[i]]) {
      return false;
    }
    seen[board[i]] = true;
  }

  // Redundant because pigeon-hole-principle, but check anyway
  for (int i = 0; i < BOARD_SIZE; i++) {
    if (!seen[i]) {
      return false;
    }
  }

  return true;
}

std::istream& operator>>(std::istream& is, Board& board) {
  for (int i = 0; i < BOARD_SIZE; i++) {
    if (!is.good()) {
      is.setstate(std::istream::failbit);
      break;
    }
    if (i > 0 && is.get() != ',') {
      is.setstate(std::istream::failbit);
      break;
    }
    int numeric;
    is >> numeric;
    board.board[i] = numeric;
  }
  if (!board.is_valid()) {
    is.setstate(std::istream::failbit);
  }
  return is;
}