convert-1d-array-into-2d-array.js

// 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.

// Link: https://leetcode.com/problems/convert-1d-array-into-2d-array/description/

//1st soln O(n)

var construct2DArray = function(original, m, n) {
    let res = [];
    if(original.length/n > m || original.length < m || original.length < m*n) return res;

    let eleArr = [];
    for(let i = 0; i<original.length; i++) {
        eleArr.push(original[i]);
        if(eleArr.length === n) {
            res.push(eleArr);
            eleArr = [];    
        }
    }

    return res;
};