Python program to find the group sum till each K in a list

Python program to find the group sum till each K in a list

Let's break down the problem:

Given a list of numbers and a number K, you want to compute the cumulative sum of elements at every Kth position.

For example, given the list [1, 2, 3, 4, 5, 6, 7] and K = 3, the result should be the sum of every 3 elements: [6, 15, 22]. Here's the breakdown:

  • First 3 elements: 1 + 2 + 3 = 6
  • Next 3 elements: 4 + 5 + 6 = 15
  • Last elements (less than 3 but whatever remains): 7 = 7 So, the cumulative sum would be 6, 6+15, 6+15+7 which results in 6, 21, 28.

Tutorial:

  1. Loop through the List:

    • Start iterating through the list. For every Kth element, compute the sum and add it to the previous sums.

  2. Calculate Sum:

    • Compute the sum of every K elements using list slicing.

  3. Handle Remaining Elements:

    • If the number of elements is not a multiple of K, then the last group will have fewer than K elements. Handle this by computing the sum of the remaining elements.

Python Program:

def group_sum_k(nums, k): # Calculate the number of groups groups = len(nums) // k + (1 if len(nums) % k else 0) # Compute the sum for each group sums = [sum(nums[i*k : (i+1)*k]) for i in range(groups)] # Calculate the cumulative sum for i in range(1, len(sums)): sums[i] += sums[i-1] return sums # Test numbers = [1, 2, 3, 4, 5, 6, 7] k = 3 result = group_sum_k(numbers, k) print(f"Cumulative sum at every {k}th position: {result}")

When you run the program with the provided test list and k=3, you should get:

Cumulative sum at every 3th position: [6, 21, 28]

Explanation:

  • The group_sum_k function first determines the number of groups using integer division and the modulo operator.
  • Then, using a list comprehension, the sum of every K elements is computed.
  • The cumulative sum is then computed in a subsequent loop.
  • The result is then printed out.

This method provides an efficient way to compute the group sum till each K in a list.

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