logo CodeStepByStep logo

mergeDigitPairs

Language/Type: C++ recursion

Write a recursive function named mergeDigitPairs that accepts an integer parameter n and returns the integer formed by combining each pair of digits from n into a single digit that is their sum. For example, if passed the number 1234, you should combine the digits 12 into 1+2 or 3, and combine the digits 34 into 3+4 or 7, leading to a returned result of 37.

If adding a given pair of digits produces a two-digit number, repeat the process until you have a single-digit number to replace the original pair. For example, if passed the number 1168, the 11 becomes 1+1 or 2, but the 68 becomes 6+8 or 14, so we merge them again by saying that 14 is 1+4 or 5, so the pair 68 turns into 5, leading to an overall result of 25.

If passed a number with an odd number of digits, the first (most significant) digit is left untouched. For example, the number 13372 becomes 169 because the 3+3 becomes 6 and the 7+2 becomes 9. If passed a negative number, perform the same process as usual but return a negative result. For example, when passed -1234, return -37. If passed a single-digit number, simply return that number itself.

The following table shows several calls and their expected return values:

Call Return Value
mergeDigitPairs(1234) 37
mergeDigitPairs(3186507) 3927
mergeDigitPairs(-52874) -512
mergeDigitPairs(88888888) 7777
mergeDigitPairs(20581974) 2412
mergeDigitPairs(0) 0
mergeDigitPairs(6) 6
mergeDigitPairs(6) -5

Constraints: Do not declare any global variables. Also, do not use any loops; you must use recursion. Do not use a string to solve this problem. (For example, do not convert n into a string.) You are allowed to define other "helper" functions if you like; they are subject to these same constraints.

Type your C++ solution code here:


This is a function exercise. Write a C++ function as described. Do not write a complete program; just the function(s) above.

You must log in before you can solve this problem.

Log In

Need help?

If you do not understand how to solve an exercise or why your solution doesn't work, please contact your TA or instructor.
If something seems wrong with the site (errors, slow performance, incorrect tests, etc.), please

Is there a problem? Contact a site administrator.

©, all rights reserved.