package q36

func validateCol(board [][]byte, col int) bool {
	var present [10]bool
	for i := range 9 {
		c := board[i][col]
		if c != '.' {
			if present[c-'0'] {
				return false
			}
			present[c-'0'] = true
		}
	}
	return true
}

func validateRow(board [][]byte, row int) bool {
	var present [10]bool
	for i := range 9 {
		c := board[row][i]
		if c != '.' {
			if present[c-'0'] {
				return false
			}
			present[c-'0'] = true
		}
	}
	return true
}

func validateBox(board [][]byte, box int) bool {
	xOffset := (box % 3) * 3
	yOffset := (box / 3) * 3

	var present [10]bool
	for i := range 9 {
		x := xOffset + i%3
		y := yOffset + i/3
		c := board[y][x]
		if c != '.' {
			if present[c-'0'] {
				return false
			}
			present[c-'0'] = true
		}
	}
	return true
}

func validate(board [][]byte) bool {
	for i := range 9 {
		if !validateCol(board, i) || !validateRow(board, i) || !validateBox(board, i) {
			return false
		}
	}
	return true
}

func isValidSudoku(board [][]byte) bool {
	return validate(board)
}

var _ = isValidSudoku