Find largest number possible from set of given numbers

Given an array of integers, find the largest number possible. The numbers should be appended to each other in any order to form the largest number. Return this number in string format.

Example Solution

Let array arr equal to [ 10, 68, 75, 7, 21, 12 ]. The largest number formed by appending is 77568211210, therefore the solution should return the string 77568211210.