# Issue

This Content is from Stack Overflow. Question asked by Daniel

I am given a string, and I have to calculate the sum of of each distance of bit pairs where both bits are 1.

For example the given string of 100101 would have the distance of 10
100101 (3)
100101 (5)
100101 (2)

Therefore the sum of distances is 3+5+2=10.

My current code is the following, I can’t really solve what’s wrong, and how should I approach the problem.

``````def pairs(s):
count = 0
for i in range(len(s)):
if s[i] == '1':
for j in range(i+1, len(s)):
if s[j] == '1':
count += 1
return count

if __name__ == "__main__":
print(pairs("100101")) #10
``````

I have also tried to store the 1’s in a list, but can’t manage to calculate the distance.

# Solution

The following should do it:

``````def pairs(s):
count = 0
for i in range(len(s)):
if s[i] == '1':
dist = 0
for j in range(i+1, len(s)):
dist += 1
if s[j] == '1':
count += dist
return count

if __name__ == "__main__":
print(pairs("100101")) #10
``````

``` This Question was asked in  StackOverflow by  Daniel and Answered by Axel Kemper It is licensed under the terms of
CC BY-SA 2.5. - CC BY-SA 3.0. - CC BY-SA 4.0.```