Introduction to functions, loops, Intro to recursion and time complexity.

Problem given a integer you need to return the sum of digits recursively. Suppose 999 -> 27 -> 9

We will build from scratch, maximum integer is 9...(9) count. So we can always get the single number in maximum of 3 steps, we will try with dirty code and start cleaning and make it reusable and modular.

General trick to count digits is implemented using while loop, but there is a for loop implementation

    for (n; n != 0; n = n/10){
        r = n % 10;
        sum = sum + r;
    }
    

• no recursion
• functions
• no repeatable code