# 2677. Chunk Array

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

[2677. Chunk Array](https://leetcode.com/problems/chunk-array/)

### 題目描述

Given an array `arr` and a chunk size `size`, return a **chunked** array. A **chunked** array contains the original elements in `arr`, but consists of subarrays each of length `size`. The length of the last subarray may be less than `size` if `arr.length` is not evenly divisible by `size`.

You may assume the array is the output of `JSON.parse`. In other words, it is valid JSON.

Please solve it without using lodash's `_.chunk` function.

### 範例

**Example 1:**

Input: arr = [1,2,3,4,5], size = 1
Output: [[1],[2],[3],[4],[5]]
Explanation: The arr has been split into subarrays each with 1 element.

**Example 2:**

Input: arr = [1,9,6,3,2], size = 3
Output: [[1,9,6],[3,2]]
Explanation: The arr has been split into subarrays with 3 elements. However, only two elements are left for the 2nd subarray.

**Example 3:**

Input: arr = [8,5,3,2,6], size = 6
Output: [[8,5,3,2,6]]
Explanation: Size is greater than arr.length thus all elements are in the first subarray.

**Example 4:**

Input: arr = [], size = 1
Output: []
Explanation: There are no elements to be chunked so an empty array is returned.

**Constraints**:

- `arr is a valid JSON array`
- 2 <= `JSON.stringify(arr).length` <= 10⁵
- `1 <= size <= arr.length + 1`

### 解答

#### TypeScript

`slice` 解

function chunk<T = unknown>(arr: T[], size: number): T[][] {
  const chunksCount = Math.ceil(arr.length / size);
  const chunkedArray: T[][] = [];

  for (let i = 0; i < chunksCount; i++) {
    chunkedArray.push(arr.slice(i * size, i * size + size));
  }

  return chunkedArray;
}

> [name=Sheep][time=Thur, May 25, 2023]

#### TypeScript

`reduce` 解

function chunk<T = unknown>(arr: T[], size: number): T[][] {
  return arr.reduce((chunkedArray: T[][], currentElement, index) => {
    const chunkIndex = Math.floor(index / size);

    if (!chunkedArray[chunkIndex]) {
      chunkedArray[chunkIndex] = [];
    }

    chunkedArray[chunkIndex].push(currentElement);

    return chunkedArray;
  }, []);
}

> [name=Sheep][time=Thur, May 25, 2023]

### Reference

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