I implement this sorting program in c . Why this is not working?

Question

#include <stdio.h>
int main() {
    int arr[5];
   
    for(int i=0; i<5; i++)
        scanf("%d",&arr[i]); 

    for(int i=0; i<5; i++)
    {
        int m=arr[i];
        for(int j=i+1; j <5; j++)
        {
            if(m>arr[j])
            {
                arr[i]=arr[j];
                arr[j]=m;
            }
       }
   }

   for(int i=0; i<5; i++)
       printf("%d ",arr[i]);
   return 0;
}

Why is this sorting program not working? Where is this program wrong? This program not sorting the array. Where is it wrong?

Answer 1

The problem is this if statement

if(m>arr[j])
{
    arr[i]=arr[j];
    arr[j]=m;
}

that does not update the value of the variable m.

You need to write

if(m>arr[j])
{
    arr[i]=arr[j];
    arr[j]=m;
    m = arr[i];
}

In fact the variable m declared before the inner for loop is redundant. You could just write without using the variable m

if ( arr[j] < arr[i] )
{
    int tmp = arr[i];
    arr[i] = arr[j];
    arr[j] = tmp;
}

The loops could be more efficient if to swap elements in the array only one time. For example

for ( int i = 0; i < 5; i++ )
{
    int m = i;

    for ( int j = i + 1; j < 5; j++ )
    {
        if ( arr[j] < arr[m] )
        {
            m = j;
        }
    }

    if ( m != i )
    {
        int tmp = arr[i];
        arr[i] = arr[m];
        arr[m] = tmp;
    } 
}

You could write a separate function. For example

void selection_sort( int a[], size_t n )
{
    for ( size_t i = 0; i < n; i++ )
    {
        size_t m = i;

        for ( size_t j = i + 1; j < n; j++ )
        {
            if ( a[j] < a[m] )
            {
                m = j;
            }
        }

        if ( m != i )
        {
            int tmp = a[i];
            a[i] = a[m];
            a[m] = tmp;
        } 
    }
}

and call it like

selection_sort( arr, 5 );