Formatted question description: https://leetcode.ca/all/2022.html

# 2022. Convert 1D Array Into 2D Array (Easy)

You are given a **0-indexed** 1-dimensional (1D) integer array `original`

, and two integers, `m`

and `n`

. You are tasked with creating a 2-dimensional (2D) array with ` m`

rows and `n`

columns using **all** the elements from `original`

.

The elements from indices `0`

to `n - 1`

(**inclusive**) of `original`

should form the first row of the constructed 2D array, the elements from indices `n`

to `2 * n - 1`

(**inclusive**) should form the second row of the constructed 2D array, and so on.

Return *an *`m x n`

* 2D array constructed according to the above procedure, or an empty 2D array if it is impossible*.

**Example 1:**

Input:original = [1,2,3,4], m = 2, n = 2Output:[[1,2],[3,4]]Explanation:The constructed 2D array should contain 2 rows and 2 columns. The first group of n=2 elements in original, [1,2], becomes the first row in the constructed 2D array. The second group of n=2 elements in original, [3,4], becomes the second row in the constructed 2D array.

**Example 2:**

Input:original = [1,2,3], m = 1, n = 3Output:[[1,2,3]]Explanation:The constructed 2D array should contain 1 row and 3 columns. Put all three elements in original into the first row of the constructed 2D array.

**Example 3:**

Input:original = [1,2], m = 1, n = 1Output:[]Explanation:There are 2 elements in original. It is impossible to fit 2 elements in a 1x1 2D array, so return an empty 2D array.

**Example 4:**

Input:original = [3], m = 1, n = 2Output:[]Explanation:There is 1 element in original. It is impossible to make 1 element fill all the spots in a 1x2 2D array, so return an empty 2D array.

**Constraints:**

`1 <= original.length <= 5 * 10`

^{4}`1 <= original[i] <= 10`

^{5}`1 <= m, n <= 4 * 10`

^{4}

**Similar Questions**:

## Solution 1. Brute Force

```
// OJ: https://leetcode.com/problems/convert-1d-array-into-2d-array/
// Time: O(K) where `K` is the length of the original array
// Space: O(1)
class Solution {
public:
vector<vector<int>> construct2DArray(vector<int>& A, int m, int n) {
if (A.size() != m * n) return {};
vector<vector<int>> ans(m, vector<int>(n));
int k = 0;
for (int i = 0; i < m; ++i) {
for (int j = 0; j < n; ++j) {
ans[i][j] = A[k++];
}
}
return ans;
}
};
```

## Discuss

https://leetcode.com/problems/convert-1d-array-into-2d-array/discuss/1499226/C%2B%2B-Brute-Force