Salesforce MTS 2.8 YOE

I was invited to the Salesforce office for their hirin event on 10 september after clearing a hackerrank assessment which was of easy-medium difficulty.

Questions in Hackerrank Assessment:

1. Given an string array of integers, return the largest integer that can be formed with the numbers in the array
2. Given a 2D array, return a sub array which is having the maximum sum out of all sub arrays, if 2 sub arrays have same sum, return the smaller subarray

Questions asked in the F2F Round:

1. Find the first non-repeating character in a string (Expected TC: O(n))

2. Given an integer array, keep all the zeroes at the end of the array and maintain the order of other elements ith respect to the original array Expected TC O(n) SC O(1)

Gave the optimal approaches for both, but could not implement the code correctly as I wasn't well prepared.
Result: Rejected