I am working on a problem about building a min heap from an array. I have 2 approaches - the first is recursion and the second is using a while loop. The recursion approach passed the tests on the online grader, but the while loop version doesn't seem to work. I generated some random stress tests in my code below and found that the 2 methods gave different answers as well.

May I know what's the mistake in my second method? The question is as follows:

Input Format. The first line of the input contains single integer