Selection Sort in C

Hello Everyone, Can anyone suggest me tutorial of selection sort where I can check the implementation code to selection sort in C?

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selection sort in c - Google Search

Third hit for me looks OK:

Selection sort in C | Programming Simplified

Code:

---

#include <stdio.h>

#define ub(x) sizeof(x)/sizeof(x[0])

int arr[] = { 64, 25, 12, 4, 101, 22, 11 };
int smallest = 0, selection = 0;

void getSmallest() { 
  smallest = 0;
  for (int y=0; y<ub(arr); y++) {
    if (arr[y] < smallest || smallest == 0) {
      if (arr[y] != 0) {
        smallest = arr[y];
        selection = y;
      }
    }
  }
  printf( "%i,", smallest );
}

int main( int argc, char *argv[] ) {
 
  for (int i=0; i<ub(arr); i++) {
    getSmallest();
    arr[selection] = 0;
  }

  printf( "\n" );
  return 0;
}

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Selection sort... walk through the first element to the last but one (i). Inside that loop, walk to the second element to the last (j). Compare element at position i to the element at position j. If your criteria is "less than", then if element j is "less than" element i, swap them. That's it.

Code:

---

void selectionSort(
    void *ptr,  // pointer to array
    size_t nelems, // num of elements in array
    size_t size,  // size of each element
    int (*criteria)(void *, void *) // sorting criteria.
  )
{
  size_t i, j;
  void *tmp = malloc( size );

  for ( i = 0; i < nelems - 1; i++ )
    for ( j = 1; j < nelems; j++ )
      if ( criteria( ptr + i*size, ptr + j*size ) > 0 )
      {
        memcpy( tmp, ptr + i*size, size );
        memcpy( ptr+i*size, ptr+j*size, size );
        memcpy( ptr+j*size, tmp, size );
      }

  free( tmp );
}

---

criteria is pointer to a function which returns -1, 0 or 1 (if 1, swap is made).

PS: void pointers (by ISO) behave as if they were char pointers, with pointer arithmetic.

Usage:

Code:

---

int a[] = { 1, 10, 3, 4, -1, -13, 7 };

int criteria( void *a, void *b )
{ return (*(int *)a > *(int *)b) - (*(int *)a < *(int *)b); }

...
selectionSort( a, sizeof a/sizeof a[0], sizeof a[0], criteria );

---

Code:

---

#include <stdio.h>

#define ub(x) sizeof(x)/sizeof(x[0])

void selectionsort( int array[], int arraySize ) {
 
 for (int j=0; j<arraySize; j++) {
 
  int smallest = 0, selection = 0;
  int tmpBase = array[j];

  for (int i=j; i<arraySize; i++) {
    if (smallest == 0 || smallest > array[i]) {
      smallest = array[i]; selection = i;
    }   
  }
 
  array[j] = array[selection];
  array[selection] = tmpBase;

 }

}

int main( int argc, char *argv[] ) {

  int arr[] = { 64, 25, 12, 4, 101, 22, 11 }; 
  selectionsort( arr, ub(arr) );

  for (int i=0; i<ub(arr); i++) {
    printf( "%i,", arr[i] );
  }

  printf( "\n" );
  return 0;
}

---

Thanks for providing a sample. I have checked this on <<spam site removed>>