DAA MERGESORT

#include<stdio.h>

void mergesort(int a[],int i,int j);
void merge(int a[],int p,int q,int r);
int n;

void main(){
int a[10],i;
    printf("Enter no of elements:");
    scanf("%d",&n);
    printf("Enter array elements:");
    for(i=0;i<n;i++)
        scanf("%d",&a[i]);

    mergesort(a,0,n-1);


 printf("\nSorted array is :");
    for(i=0;i<(n);i++)
        printf("%d ",a[i]);


}

void mergesort(int a[],int p,int r){
int q;
if(p<r){
q=((p+r)/2);
mergesort(a,p,q);
mergesort(a,q+1,r);
merge(a,p,q,r);
}
}


void merge(int a[],int p,int q,int r){
int b[30];
int i,j,k,c;

i=p;  //beginning index
j=q+1;
k=0; //will use it to uterate through b array

while(i<=q && j<=r)    //while elements in both lists
    {
        if(a[i]<a[j])   //checking two subarrays(metaphorically) (array is still same)
            b[k++]=a[i++];
        else
            b[k++]=a[j++];
    }

while(i<=q){ //copy remaining elements to auxiliarry array from first half of original array as it is still unsorted(after the half)
 b[k++]=a[i++];
}

while(j<=r)
 b[k++]=a[j++];

for(i=p,j=0;i<=r;i++,j++)
        a[i]=b[j];


}