Using heap sort, append an array elements

Question

I have given an array int A[] = {12,10,9,2,11,8,14,3,5}; In this array, 1st 4 elements(from index 0 to index 3) follow max heap condition. But last 5 elements(index 4 to index 8) don't follow max heap condition. So, I have to write a code so that the whole array follow max heap condition.

I have given a function call max_heap_append(A,3,8); and I have to use it in my code to write the program. It is an assignment so I have to follow the instruction.

I have written this code bellow but when I run the program, nothing happens.

#include <stdio.h>
#include <stdlib.h>

void swap(int * a, int * b )
{
    int temp;

    temp = *a;
    *a = *b;
    *b = temp;

}

void heapify( int A[], int q, int i) 
{
    int largest = i;
    int l = 2 * i + 1 ;
    int r = 2 * i + 2;

    if( l < q && A[l] > A[largest])
    {
        largest = l;
    }
    if( r < q && A[r] > A[largest])
    {
        largest = r;
    }
    if( largest != i)
    {
        swap( &A[i] , &A[largest]);
        heapify(A, q, largest);
    }
}



void max_heap_append(int A[], int p , int q) 
{
    int i;

    for( i = q / 2 -1; i >= 0; i--)  
    {
        heapify( A , q , i);
    }
    // sort the heap
    for( i = q; i>= 0; i--)
    {
        swap(&A[0] , &A[i]);

        heapify(A, i, 0);
    }


}
 void printA(int A[], int q)
 {
     int i;
     for( i = 0; i <= q; i++)
     {
         printf("%d", A[i]);

     }
     printf("%d\n");
 }


int main()
{

    int A[] = {12,10,9,2,11,8,14,3};

    max_heap_append(A,3,8);

    printf("Sorted: ");

    printA(A, 8);

    return 0;
}

Golam Mazid Sajib · Accepted Answer · 2020-04-13 18:25:13Z

1

Its not followed heapify from 0 to 3 index.. so u need to heapify all. there is some mistake. if your array size is 8 then u can not excess a[8], you can access a[0] to a[7]. so you need to iterate from 0 to 7.

Try with this:

#include <stdio.h>
#include <stdlib.h>

void swap(int * a, int * b )
{
    int temp;

    temp = *a;
    *a = *b;
    *b = temp;

}

void heapify( int A[], int q, int i)
{
    int largest = i;
    int l = 2 * i + 1 ;
    int r = 2 * i + 2;

    if( l < q && A[l] > A[largest])
    {
        largest = l;
    }
    if( r < q && A[r] > A[largest])
    {
        largest = r;
    }
    if( largest != i)
    {
        swap( &A[i] , &A[largest]);
        heapify(A, q, largest);
    }
}



void max_heap_append(int A[], int p , int q)
{
    int i;

    for( i = q-1; i >= 0; i--)
    {
        heapify( A , q , i);
    }
    // sort the heap
    for( i = q-1; i>= 0; i--)
    {
        swap(&A[0] , &A[i]);

        heapify(A, i, 0);
    }


}
void printA(int A[], int q)
{
    int i;
    for( i = 0; i < q; i++)
    {
        printf("%d ", A[i]);

    }
    printf("\n");
}


int main()
{

    int A[] = {12,10,9,2,11,8,14,3};

    max_heap_append(A,3,8);

    printf("Sorted: ");

    printA(A, 8);

    return 0;
}

answered Apr 13, 2020 at 18:25

Golam Mazid Sajib

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1 Comment

Jim Mischel Over a year ago

That's fine, although you're doing more work than necessary. You can start the first loop at (q-1)/2, because the items below that are at the leaf level and can't possibly move down.

bruno · Accepted Answer · 2020-04-13 18:41:06Z

You have several problems in your code

printA

One is/can be indicated by the compiler, in printA :

printf("%d\n");

‘%d’ expects a matching ‘int’ argument, but there no no argument

It is easy to guess you just wanted to print a newline, so that line can be replaced by

putchar('\n');

Still in printA you print the numbers without a separator, the result is not usable, for instance do

printf("%d ", A[i]);

When I look at the call of printA in main the parameter n is the number of elements in A, so the end test of the for is invalid because you try to print a value out of the array, the loop must be :

for( i = 0; i < q; i++)

max_heap_append

in the second for the index i can value 0, in that case you swap the first element of the array with itself, that has no sense and the same for the call of heapify with the 2 last arguments valuing 0

When you call that function in main the parameter q receive the number of elements in the array, which is also the first value of i still in that second for and &A[i] is out of the array. You need to replace that line by

for( i = q-1; i> 0; i--)

If I do all these changes :

Compilation and execution :

bruno@bruno-XPS-8300:/tmp$ gcc -g -Wall h.c
bruno@bruno-XPS-8300:/tmp$ ./a.out
Sorted: 2 3 8 9 10 11 12 14 
bruno@bruno-XPS-8300:/tmp$

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