help me understand this

Question

#include <stdio.h>
int main(void) {
// your code goes here
int t;
int n,a[1000001]={0};
scanf("%d",&t);
while(t--)
{
scanf("%d",&n);
a[n]++;
}
for (int i=0;i<1000001;i++)
{
while(a[i]>0)
{
printf("%d\n",i);
a[i]--;
}
}
return 0;
}

Answer 1

That implements a counting sort algorithm( https://en.wikipedia.org/wiki/Counting_sort ).

1. All array elements are initialized to 0. In other words, each and every element in a is initialized to 0.
2. A number t is read in. This is the number of remaining numbers to read in and sort.
3. t numbers are read in and added to the counts in array a. Each number must be between 0 and 1 million to fit the boundaries of array a.
4. The original numbers are printed in sorted order.

Answer 2

Josh Greig yeah , I'm just trying to understand how the sorting works actually, how is this comparing of elements works?

Answer 3

Rajesh wrote, "Josh Greig yeah , I'm just trying to understand how the sorting works actually, how is this comparing of elements works?"

Response:

Counting sort doesn't rely on comparisons. It isn't a comparison-based sort. Randomly accessing each array element at a given index is what happens instead of comparing elements.

Check this video for more explanation of how counting sort works:
https://www.youtube.com/watch?v=OKd534EWcdk

Bucket sort works in a similar way: https://en.wikipedia.org/wiki/Bucket_sort