We want to implement a method that reverses the digits in an integer. For example, reverseDigits(3456) should yield 6543.

Use a recursive helper method reverseDigitsHelper. Here is a typical computation.

reverseDigitsHelper(3456, 0) 
= reverseDigitsHelper(345, 6) 
= reverseDigitsHelper(34, 65) 
= reverseDigitsHelper(3, 654) 
= reverseDigitsHelper(0, 6543) 
= 6543