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calculatePrefixSum

The calculatePrefixSum function calculates the sum of a subarray within a given list of numbers up to a specified index. This is useful for operations where you need the cumulative sum up to a certain point in the array.

Function Signature#

const calculatePrefixSum = (lengthList: number[], index: number) => number;

Parameters#

lengthList: number[]: An array of numbers. The function will calculate the sum of the elements up to the specified index.

index: number: The index up to which the sum should be calculated. This index is inclusive.

Returns#

number: The sum of the elements in the array from the start up to the specified index.

Example Usage#

Example 1: Basic Usage#

const lengthList = [3, 4, 2];const index = 1;const result = calculatePrefixSum(lengthList, index);console.log(result); // 출력: 7

This example takes the sum of the first two elements of the array [3, 4], resulting in 7.

Explanation#

  1. Array Slicing: The function uses slice(0, index + 1) to create a subarray that includes elements from the start of the array up to and including the specified index.

  2. Cumulative Sum: The reduce method is then used to sum the values in the sliced array. The initial value of the accumulator (acc) is set to 0.

  3. Return Value: The function returns the total sum of the specified subarray.