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The selection sort algorithm sorts an array by repeatedly finding the minimum element (considering ascending order)  from unsorted part and putting it at the beginning. The algorithm maintains two subarrays in a given array.

1) The subarray which is already sorted.
2) Remaining subarray which is unsorted.

In every iteration of selection sort, the minimum element (considering ascending order) from the unsorted subarray is picked and moved to the sorted subarray.

C program for selection sort to sort numbers. This code implements selection sort algorithm to arrange numbers of an array in ascending order. With a little modification, it will arrange numbers in descending order.

#include <stdio.h>
 
int main()
{
   int array[100], n, c, d, position, swap;
 
   printf("Enter number of elements\n");
   scanf("%d", &n);
 
   printf("Enter %d integers\n", n);
 
   for ( c = 0 ; c < n ; c++ )
      scanf("%d", &array[c]);
 
   for ( c = 0 ; c < ( n - 1 ) ; c++ )
   {
      position = c;
 
      for ( d = c + 1 ; d < n ; d++ )
      {
         if ( array[position] > array[d] )
            position = d;
      }
      if ( position != c )
      {
         swap = array[c];
         array[c] = array[position];
         array[position] = swap;
      }
   }
 
   printf("Sorted list in ascending order:\n");
 
   for ( c = 0 ; c < n ; c++ )
      printf("%d\n", array[c]);
 
   return 0;
}

Enter number of elements
8
Enter 8 integers
98
78
7
9
7
6
6
5
Sorted list in ascending order:
5
6
6
7
7
9
78
98
Press any key to continue . . .

Time Complexity: O(n²) as there are two nested loops.

Auxiliary Space: O(1)
The good thing about selection sort is it never makes more than O(n) swaps and can be useful when the memory write is a costly operation.

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