You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: Solution.go
    path of file: ./repos/awesome-golang-algorithm/leetcode/1-100/0037.Sudoku-Solver
    
    the code of the file until where you have to start completion: package Solution

func solveSudoku(board [][]byte) {
	solve(board, 0)
}

/* k 是把 board 转换成一维数组后，元素的索引值 */
func solve(board [][]byte, k int) bool {
	if k == 81 {
		return true
	}

	r, c := k/9, k%9
	if board[r][c] != '.' {
		return solve(board, k+1)
	}

	/* bi, bj 是 rc 所在
    
func solve(board [][]byte, k int) bool {
	if k == 81 {
		return true
	}

	r, c := k/9, k%9
	if board[r][c] != '.' {
		return solve(board, k+1)
	}

	/* bi, bj 是 rc 所在块的左上角元素的索引值 */
	bi, bj := r/3*3, c/3*3

	// 按照数独的规则，检查 b 能否放在 board[r][c]
	isValid := func(b byte) bool {
		for n := 0; n < 9; n++ {
			if board[r][n] == b ||
				board[n][c] == b ||
				board[bi+n/3][bj+n%3] == b {
				return false
			}
		}
		return true
	}

	for b := byte('1'); b <= '9'; b++ {
		if isValid(b) {
			board[r][c] = b
			if solve(board, k+1) {
				return true
			}
		}
	}

	board[r][c] = '.'

	return false
}