Question

For example i want to find numbers including 2,7 from 1 to 7000 without converting string.
2 7 12 17 … 20 21 22 23…7000
Is there a good algorithm with math?
thank you in advance…

Answer 1

Something like that

while ( n > 0 ) {
   digit = n % 10;
   // check the digit
   n = n / 10;
}

Example with 523

1. In the first iteration you will have digit = 3 (123 % 10)
2. In the second iteration you will have digit = 2 (12 % 10)
3. In the third digit = 5 (5 % 10)