Running Sum of 1d Array

📘 Problem Statement

You’re given an array nums. You need to return a new array runningSum such that:

runningSum[i] = sum(nums[0] + nums[1] + ... + nums[i])

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🔍 Example

Example 1 Input: nums = [1, 2, 3, 4]

Output: [1, 3, 6, 10]

Explanation:

runningSum[0] = 1
runningSum[1] = 1 + 2 = 3
runningSum[2] = 3 + 3 = 6
runningSum[3] = 6 + 4 = 10

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🛠️ Solution - Using Prefix Sum

The problem is the essential crux of Prefix Sum. Idea is to loop through the original array and maintain a cumulative sum in a new array. Here is a quick implementation of the solution:

def runningSum(nums):
    result = []
    current_sum = 0
    for num in nums:
        current_sum += num
        result.append(current_sum)
    return result