Basic C++ Question

Question

Primary U.S. interstate highways are numbered 1-99. Odd numbers (like the 5 or 95) go north/south, and evens (like the 10 or 90) go east/west. Auxiliary highways are numbered 100-999, and service the primary highway indicated by the rightmost two digits. Thus, I-405 services I-5, and I-290 services I-90. Note: 200 is not a valid auxiliary highway because 00 is not a valid primary highway number.

Given a highway number, indicate whether it is a primary or auxiliary highway. If auxiliary, indicate what primary highway it serves. Also indicate if the (primary) highway runs north/south or east/west.

Ex: If the input is:

90

The output is:

I-90 is primary, going east/west.

Ex: If the input is:

290

The output is:

I-290 is auxiliary, serving I-90, going east/west.

Ex: If the input is:

0

The output is:

0 is not a valid interstate highway number.

Ex: If the input is:

200

The output is:

200 is not a valid interstate highway number.

See Wikipedia for more info on highway numbering.

Answer 1

The approach you want to take is as follows.

If the number input is between 1 and 99 inclusive, it is a primary interstate. If it is odd (number % 2 == 1), it goes north/south, and if it is even (number % 2 == 0), it goes east/west.

If the number is greater than 999, it is automatically invalid.

If the number is between 100-999, check if the last two digits are equal to zero (number % 100 == 0). If so, it is invalid. Otherwise, the result of (number % 100) will be the interstate number it services, and you can use that to check if it is going north/south or east/west.