Leetcode 2138: Divide a String Into Groups of Size k

In this problem, we divide a String into a list of substrings of size k. In the last String is not of size k, we complete the string with a fill character until the string is of size k.

Example:
s = "abcdef", k = 4, fill = 'x'
Return: ["abcd", "efxx"]

• First, we want all the substrings of size k by using the function substring in a loop. In the loop we will keep track of an index currIndex starting at 0 and incremented of k after each iteration.
• The loop stops when currIndex + k > n, with n the size of the input String.
• When the loop is done, we need to find out if the last string is incomplete, in which case we need to fill the string using fill.
• If the current index currIndex is less than n, then we need to create a filler string by adding the fill character k — (n — currIndex) times, then adding it to the remaining String.
• We create a function repeatChar for readability, that returns a String consisting of one char fill repeated repeat times.
• In the algorithm, we add all the Strings to a List (for instance ArrayList), that we convert to an array at the end to fit with the problem output.

In summary:

Main algorithm ideas