CODEWITHSUNDEEP
python-3.xalgorithmsortingdata-structures
Daniel
Daniel

Reputation: 186

Distance of Bit pairs

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.

Upvotes: 1

Views: 188

Answers (2)

Andrej Kesely
Andrej Kesely

Reputation: 195553

Try itertools.combinations on indices where the char == 1:

from itertools import combinations

s = "100101"

indices = [i for i, ch in enumerate(s) if ch == "1"]
print(sum(b - a for a, b in combinations(indices, 2)))

Prints:

10

Upvotes: 1

Axel Kemper
Axel Kemper

Reputation: 11322

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

Upvotes: 1

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