Leetcode#37 Sudoku Solver

原题地址

回溯，没啥好说的

bool row[9][9];
bool col[9][9];
bool grid[9][9];
bool mark[9][9];

bool solve(vector<vector<char> > &board, int r, int c) {
  if (r == 9)
    return true;
  if (mark[r][c])
    return solve(board, r + (c + 1) / 9, (c + 1) % 9);
  for (int i = 0; i < 9; i++) {
    if (!row[r][i] && !col[c][i] && !grid[(r / 3) * 3 + c / 3][i]) {
      row[r][i] = col[c][i] = grid[(r / 3) * 3 + c / 3][i] = true;
      board[r][c] = i + '1';
      if (solve(board, r + (c + 1) / 9, (c + 1) % 9))
        return true;
      board[r][c] = '.';
      row[r][i] = col[c][i] = grid[(r / 3) * 3 + c / 3][i] = false;
    }
  }

  return false;
}

void solveSudoku(vector<vector<char> > &board) {
  memset(row, 9 * 9 * sizeof(bool), false);
  memset(col, 9 * 9 * sizeof(bool), false);
  memset(grid, 9 * 9 * sizeof(bool), false);
  memset(mark, 9 * 9 * sizeof(bool), false);

  for (int r = 0; r < 9; r++)
    for (int c = 0; c < 9; c++)
      if (board[r][c] != '.') {
        row[r][board[r][c] - '1']
          = col[c][board[r][c] - '1']
          = grid[(r / 3) * 3 + c / 3][board[r][c] - '1']
          = mark[r][c]
          = true;
      }

  solve(board, 0, 0);
}