Fertile Mind: Apply Permutation

Apply Permutation

Write a program that takes a permutation array and a input array and reorder the input array as per the given permutation.

I can see that this seems to be a linear time problem.
We need to apply permutation inc cycle.
Start at 0 replace current position at 0 with previous input, swap previous input at current position. continue till end.
However there are multiple missing things in this solution.
As there can be multiple cycle in the same array. Therefore we need mechanism to break from cycle and then run on the next cycle.
To break the cycle we need to keep an bool index whether the position is processed or not.
and to go to next cycle we can always scan the processed array for non processed items and then start the process there.
This seems okay.
Find code here.

This question might seem simple but to implement it correctly is difficult.
Since I coded through the problem solving my code also looked tangled and complex.
After multiple debugging sessions and fixing problems. The code looked in a very bad shape.
However it passed all test cases.
Then I looked at the answer to find it to my surprise, that the code written is so much more elegant than what I had written.
However there is space optimization in the book's answer but ignoring that also the code was much more simple.
Later I refactored my code into that shape. Felt both good and bad.
Writing good code is really really difficult. I understand it now. Everyone can code but to make proper sentences in the language is the art. To write pieces that are elegant and clear and concise.
Now that I have refactored it. It look good.
Also one key insight is that whenever you feel like using an iterator that runs through all the elements in linear fashion use a for loop. and when needed to skip use continue or empty loop cycle. No need to write make complex iterator advances.
Small question lots of learning.