Week 6: Tuesday
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Q1. (50)

Write a function to recursively compute the sum of digits of a positive
integer. Please note that the function has to be recursive. Implement the
following function:
	int sum(int n) where n is the number

Next write a function that utilizes the above function to repeatedly compute
the sum of digits till the sum becomes a single-digit number. You can use
recursion again if you want. Output each intermediate sum and the final sum.

For example, for the input 98895, the successive outputs are 39 (9 + 8 + 8 + 9
+ 5), 12 (3 + 9) and 3 (1 + 2). For the input 34, the only output is 7 (3 + 4).

Write a main function to test the code.

Q2. (50)

In the main function, create an array of size 10. Input integers from the user
till a negative integer is input or the 10 elements have been filled up. Save
the number of valid entries of the array in a variable.

Now, write a recursive function to compute the maximum element of this array.
Output the maximum.