Just a quick help please

Question

I found this code in the challenge and the output has to be 18. Can anybody help me figure it out, how the output is 18 ?

https://code.sololearn.com/c1P3nkO9D7wE/?ref=app

Answer 1

If you add these lines inside the loop, you will get a better idea what's happening.
print(arr)
print(n)
So then you can see that it adds 3 again and again. Because you changed the array while you goes through them.

Arr:
0, 1, 2, 10, 10... 3, 4, 5
The pointer goes from left to right through the array but you insirt everytime 10 so it reached again again 3.
I hope it was understandable.

Answer 2

So the index of 3 is incremented by 1 after each Iteration, therefore returning the same value for n i.e 3 ?

Output = 0+1+2+3+3+3+3+3
= 18

Thank you, everyone !

Answer 3

Ipang Do you really think same would happen if we remove a member ?

sum = 0
arr = [0,1,2,3,4,5]

for n in arr:
sum += n
if n == 3:
del arr[n]
if sum > 15:
break
print(sum)
This code gives output : 0+1+2+3+5

Answer 4

Sacar,
Not with the exact same scenario, but in summary, modification to an iterable during iteration through it, brings funny unexpected result.

Answer 5

Add this line as the first line inside the for...in loop to better understand what's going on before the check of <sum> > 15

print( f'n = ({n}) sum = ({sum}) arr ={arr}' )

Answer 6

As Stefanno has already mentioned, what happens is, when loop reaches n==3 it gets stuck on that element until it is bigger than 15

You cold see for yourself what exactly happens if you run that code:

https://code.sololearn.com/c2os8forQF8g/?ref=app

Answer 7

It happened because the iterable size changes during the for...in loop due to call for insert() method.

It's kinda odd but quite the same funny symptom also happens when a member is removed from the iterable during iteration :D