# 2626. Array Reduce Transformation

###### tags: `leetcode 30 days js challenge` `Easy`

[2626. Array Reduce Transformation](https://leetcode.com/problems/array-reduce-transformation/)

### 題目描述

Given an integer array `nums`, a reducer function `fn`, and an initial value `init`, return a **reduced** array.

A **reduced** array is created by applying the following operation: `val = fn(init, nums[0])`, `val = fn(val, nums[1])`, `val = fn(val, nums[2])`, `...` until every element in the array has been processed. The final value of `val` is returned.

If the length of the array is 0, it should return `init`.

Please solve it without using the built-in `Array.reduce` method.

### 範例

**Example 1:**

Input: 
nums = [1,2,3,4]
fn = function sum(accum, curr) { return accum + curr; }
init = 0
Output: 10
Explanation:
initially, the value is init=0.
(0) + nums[0] = 1
(1) + nums[1] = 3
(3) + nums[2] = 6
(6) + nums[3] = 10
The final answer is 10.

**Example 2:**

Input: 
nums = [1,2,3,4]
fn = function sum(accum, curr) { return accum + curr * curr; }
init = 100
Output: 130
Explanation:
initially, the value is init=100.
(100) + nums[0]^2 = 101
(101) + nums[1]^2 = 105
(105) + nums[2]^2 = 114
(114) + nums[3]^2 = 130
The final answer is 130.

**Example 3:**

Input: 
nums = []
fn = function sum(accum, curr) { return 0; }
init = 25
Output: 25
Explanation: For empty arrays, the answer is always init.

**Constraints**:

- `0 <= nums.length <= 1000`
- `0 <= nums[i] <= 1000`
- `0 <= init <= 1000`

### 解答

#### TypeScript

function reduce(nums: number[], fn: Fn, init: number): number {
  let result = init;
  if (nums.length === 0) return result;

  nums.forEach((item) => (result = fn(result, item)));

  return result;
}

> [name=Sheep][time=Wed, May 10, 2023]

### Reference

[回到題目列表](https://hackmd.io/@Marsgoat/leetcode_every_day)