Answer:
[1-9][0-9]{0,2}
Step-by-step explanation:
The numbers to be matched consist of three digits with the following requirements:
- Digit 1 can take the values 1-9
- Digit 2 can take the values 0-9
- Digit 3 can take the values 0-9
- Digits 2 and 3 are optional, that is the number may consist of 1,2 or 3 digits in all.
Taking these into account, the overall regular expression can be represented as follows:
[1-9][0-9]{0,2}