Prefix sum array in Python using accumulate function

0 0 1 minute read

We are given an array, find prefix sums of given array. Examples:

Input : arr = [1, 2, 3]
Output : sum = [1, 3, 6]

Input : arr = [4, 6, 12]
Output : sum = [4, 10, 22]

A prefix sum is a sequence of partial sums of a given sequence. For example, the cumulative sums of the sequence {a, b, c, …} are a, a+b, a+b+c and so on. We can solve this problem in python quickly using accumulate(iterable) method.

Implementation:

Python3

# function to find cumulative sum of array
from itertools import accumulate
 
def cumulativeSum(input):
    print ("Sum :", list(accumulate(input)))
 
# Driver program
if __name__ == "__main__":
    input = [4, 6, 12]
    cumulativeSum(input)

Output

Sum : [4, 10, 22]

The time complexity of this cumulativeSum function is O(n), where n is the length of the input array.

The auxiliary space complexity of this function is also O(n), where n is the length of the input array.

Recommended

Solve DSA problems on GfG Practice.

Solve Problems

Feeling lost in the world of random DSA topics, wasting time without progress? It’s time for a change! Join our DSA course, where we’ll guide you on an exciting journey to master DSA efficiently and on schedule.
Ready to dive in? Explore our Free Demo Content and join our DSA course, trusted by over 100,000 zambiatek!