2022_Convert_1D_Array_Into_2D_Array.cpp

/*
2022. Convert 1D Array Into 2D Array
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 = 2
Output: [[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 = 3
Output: [[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 = 1
Output: []
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.
Constraints:
1 <= original.length <= 5 * 104
1 <= original[i] <= 105
1 <= m, n <= 4 * 104
*/
class Solution {
public:
    vector<vector<int>> construct2DArray(vector<int>& original, int m, int n) {
        if(m*n != original.size()) return {};
        vector<vector<int>> vec(m,vector<int>(n));
        int k = 0  ;
        for(int i = 0 ; i<m && k<original.size();i++)
            for(int j=0;j<n && k<original.size();j++) vec[i][j] = original[k++];
    return vec;
    }
};