The selection sort algorithm starts by comparing the first two elements of an array and replacing them if necessary. For example, if you want to sort the elements of an array in ascending order and if the first element is greater than the second, you need to swap the elements. But, if the first element is less than the second, the elements remain in their sequence. Then again the first element and the third element are compared and swapped if necessary. This process continues until the first and last element of the array is compared. This completes the first sort selection step.
If there are n elements to sort, the process mentioned above should be repeated n-1 times to get the desired result. To improve performance in the second step, the comparison starts from the second element, because after the first step, the desired number is automatically placed in the first one. Similarly, in the third step, the comparison starts from the third element, and so on. In the case of sorting in ascending order, the smallest element will be first, and in the case of sorting in descending order, the largest element will be first.
Consider in the figure the operation of the sorting algorithm by the selection method.
C program to sort items using selection sort algorithm
#include <stdio.h>
int main()
{
int data[100],i,n,steps,temp;
printf("Enter the number of elements to be sorted: ");
scanf("%d",&n);
for(i=0;i<n;++i)
{
printf("%d. Enter element: ",i+1);
scanf("%d",&data[i]);
}
for(steps=0;steps<n;++steps)
for(i=steps+1;i<n;++i)
{
if(data[steps]>data[i])
/* Чтобы отсортировать в порядке убывания, измените> на <. */
{
temp=data[steps];
data[steps]=data[i];
data[i]=temp;
}
}
printf("In ascending order: ");
for(i=0;i<n;++i)
printf("%d ",data[i]);
return 0;
}
Enter the number of elements to be sorted: 5 1. Enter element: 12 2. Enter element: 1 3. Enter element: 23 4. Enter element: 2 5. Enter element: 0 In ascending order: 0 1 2 12 23
Note:
Although this program is written in C, the selection sort algorithm can be used similarly in another programming language.
The selection sort algorithm is easy to use, but there are other sorting algorithms that perform better than selection sort. In particular, selection sort should not be used to sort a large number of items if performance matters in this program.
