Explain the process of selection sorting in C language

Selection sort is an aggressive algorithm used to find the smallest number from an array and place it in the first position. The next array to be traversed will start at the index, close to where the smallest number is placed.

The process of selection sorting

• Select the first smallest element in the list of elements and place it in the first position.

• Repeat the same operation for the remaining elements in the list until all elements are sorted.

Consider the following list -

First pass

Sm = a[0] = 30 Sm

a[1] < sm $\ square$ $\square$ 50 <30 (F) $\square$ $\square$ 30< sm $\square$ $\square$ 50 <30 (F) $\square$ $\square$ 30

a[2] < sm $\square$ $ \square$ 40 <30 (F) $\square $ $\square$ 20$\square$ Exchange a[0] with sm value< sm $\square$ $ \square$ 40 <30 (F) $\square$ $\square$ 20$\square$ 将 a[0] 与 sm 值交换

a[3] < sm $\square$ $\square $ 10 <30 (T) $\square$ $ \square$ 10< sm $\square$ $\square $ 10 <30 (T) $\square$ $\square$ 10

a[4] < sm $\square$ $\square$ 20<10 (F) $\square$ $\square 10 $< sm $\square$ $\square$ 20<10 (F) $\square$ $\square 10 美元

10 50 40 30 20

Second pass

Sm = a[1] = 50 sm

a[2] < sm $\square$ $\square$ 40 <50 (T) $\square$ 40 $\square$< sm $\square$ $\square$ 40 <50 (T) $\square$ 40 $\square$

a[3] < sm $\square$ $ \square$ 30 <40 (T) $\square$ 30 Exchange a[1] with sm value< sm $\square$ $ \square$ 30 <40 (T) $\square$ 30 将 a[1] 与 sm 值交换

a[4] < sm $\square$ $\square$ 20<30 (T) $ \square$ 20< sm $\square$ $\square$ 20<30 (T) $ \平方$ 20

10 20 40 30 50

Third pass

Sm = a[2] = 40 Sm

a[3] < sm $\ square$ $\square$ 30 <40 (T) $\square$ $\square$ 40

a[4] < sm $\square$ $\square$ 50<40 (F) $ \square$ $\square$ 30 exchange a[2] with sm value

a[3] < sm $\square$ $\square$ 30 <40 (T) $ \square$ $\square$ 40

a[4] < sm $\square$ $\square$ 50<40 (F) $\square$ $\square$ 30 Use sm value to exchange a[ 2]

10 20 30 40 50

Fourth time

Sm = a[3] = 40 Sm

a[4] < $\square$ $\square$ sm 50 <40 (F) $\square$ 40 $\square$ exchange a[3] with sm value

Procedure

Please refer to the following steps to select and sort.

for (i=0; i<n-1; i++){
   sm=i;
   for (j=i+1; j<n; j++){
      if (a[j] < a[sm])
         sm=j;
      }
      t=a[i];
      a[i] = a[sm];
      a[sm] = t;
   }
}

Example

The following is a C program for the selection sort technique −

#include<stdio.h>
int main(){
   int a[50], i,j,n,t,sm;
   printf("enter the No: of elements in the list:</p><p>");
   scanf("%d", &n);
   printf("enter the elements:</p><p>");
   for(i=0; i<n; i++){
      scanf ("%d", &a[i]);
   }
   for (i=0; i<n-1; i++){
      sm=i;
      for (j=i+1; j<n; j++){
         if (a[j] < a[sm]){
            sm=j;
         }
      }
      t=a[i];
      a[i]=a[sm];
      a[sm]=t;
   }
   printf ("after selection sorting the elements are:</p><p>");
   for (i=0; i<n; i++)
      printf("%d\t", a[i]);
   return 0;
}

Output

When the above program is executed, the following results are produced -

enter the No: of elements in the list:
4
enter the elements:
45
12
37
68
after selection sorting the elements are:
12 37 45 68

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