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g2601_2700.s2626_array_reduce_transformation.readme.md Maven / Gradle / Ivy

2626\. Array Reduce Transformation

Easy

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.

**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`