How do I print out the sum of all the digits of a given number using a recursive function

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trying to write recursive function in Python to find the sum of digits of a number. Name the function sum_of_digits. my function should use recursive algorithm. i want the function to print out the sum of all the digits of a given number. For example, sum_of_digits(343) should have a output of 10.

i know that we are supposed to add an if loop for it to be recursive

Output i'm trying to achieve: 10

What I have tried:

<pre>def sum_of_digits(n):
    if n ==  :
        return n
    else:
        return (n % 10) + sum_of_digits(n // 10)
sum_of_digits(343)

here is what i have implemented. i do not know what to compare 'n' with? i'm stuck at the first if

Posted 3-Feb-20 23:58pm

fadxo20

Updated 4-Feb-20 3:38am

v2

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Patrice T 4-Feb-20 6:08am

Where are you stuck ?

phil.o 4-Feb-20 6:35am

Do it by hand with a pen and piece of paper first. You will never learn to build an algorithm by asking other people to do it for you.

3 solutions

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CPallini · Answer 1 · 2020-02-04T00:38:00

Solution 1

Hint: at each step, you may use the modulo operator (e.g. n % 10 ) to get the last digit of the number (stop if it is 0) and add it to the sum. Then call the next step passing ( n // 10 ).

Posted 4-Feb-20 0:38am

CPallini

Comments

Richard MacCutchan 4-Feb-20 7:01am

+5; I couldn't work it out until I saw your suggestion.

CPallini 4-Feb-20 9:58am

I have to admit, recursion still doesn't come naturally to me.

Patrice T · Answer 2 · 2020-02-04T03:38:00

Solution 3

Another way to end the loop is:

PHP

if n < 10  :
    return n

Nota: Using a recursive function is good only when learning recursion. For such a problem, a loop in a function is using no more code, is faster at runtime and use less resources.

Posted 4-Feb-20 3:38am

Patrice T

Comments

CPallini 4-Feb-20 9:57am

Indeed. Have my 5.

Patrice T 4-Feb-20 9:59am

Thank you

fadxo20 · Answer 3 · 2020-02-04T03:01:00

Solution 2

def sum_of_digits(n):
    if n ==  :
        return n
    else:
        return (n % 10) + sum_of_digits(n // 10)
sum_of_digits(343)

here is what i have implemented. i do not know what to compare 'n' with? i'm stuck at the first if

Posted 4-Feb-20 3:01am

fadxo20

Comments

Richard MacCutchan 4-Feb-20 9:15am

    if n ==  0:
        return n