text: Count n digit numbers not having a particular digit | Python Implementation of above method ; Finding number of possible number with n digits excluding a particular digit ; Checking if number of digits is zero ; Checking if number of digits is one ; Checking if number of digits is odd ; Calling digitNumber function with ( digit - 1 ) / 2 digits ; Calling digitNumber function with n / 2 digits ; Calling digitNumber function Checking if excluding digit is zero or non - zero ; Initializing variables
code: mod = 1000000007 NEW_LINE def digitNumber ( n ) : NEW_LINE INDENT if ( n == 0 ) : NEW_LINE INDENT return 1 NEW_LINE DEDENT if ( n == 1 ) : NEW_LINE INDENT return 9 NEW_LINE DEDENT if ( n % 2 != 0 ) : NEW_LINE INDENT temp = digitNumber ( ( n - 1 ) // 2 ) % mod NEW_LINE return ( 9 * ( temp * temp ) % mod ) % mod NEW_LINE DEDENT else : NEW_LINE INDENT temp = digitNumber ( n // 2 ) % mod NEW_LINE return ( temp * temp ) % mod NEW_LINE DEDENT DEDENT def countExcluding ( n , d ) : NEW_LINE INDENT if ( d == 0 ) : NEW_LINE INDENT return ( 9 * digitNumber ( n - 1 ) ) % mod NEW_LINE DEDENT else : NEW_LINE INDENT return ( 8 * digitNumber ( n - 1 ) ) % mod NEW_LINE DEDENT DEDENT d = 9 NEW_LINE n = 3 NEW_LINE print ( countExcluding ( n , d ) ) NEW_LINE