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Prefix sum array in Python using accumulate function

  • Difficulty Level : Hard
  • Last Updated : 23 Dec, 2017
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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.




# 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]

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