C program for Sorting methods Quick sort and Merge sort using recursion

#include<conio.h>
#include<stdio.h>
void quick_sort(int [],int,int);
int partition(int [],int,int);
void mergesort(int a[] ,int i , int j);
void merge(int a[],int i1, int j1, int i2, int j2);
void main()
{
int a[30],n,i,op;
clrscr();
do
  {
    printf("\n1)Quick Sort\n2)Merge Sort \n3)Quit");
    printf("\nEnter your choice : ");
    scanf("%d",&op);
    switch(op)
     {
case 1: printf("\nEnter no of elements :");
scanf("%d",&n);
printf("\nEnter array elements :");
for(i=0;i<n;i++)
scanf("%d",&a[i]);
quick_sort(a,0,n-1);
printf("\nSorted array is :");
for(i=0;i<n;i++)
printf("%d  ",a[i]);
break;

case 2: printf("\nEnter no of elements :");
scanf("%d",&n);
printf("\nEnter 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]);
break;

  }
     }while(op!=3);
}
void quick_sort(int a[],int l,int u){
int j;
if(l<u)
{
j=partition(a,l,u);
quick_sort(a,l,j-1);
quick_sort(a,j+1,u);
}
}
int partition(int a[],int l,int u)
{
    int v,i,j,temp;
    v=a[l];
    i=l;
    j=u+1;
    do
    {
do
{ i++;
}while(a[i]<v && i<=u);

do
{ j--;
}while(a[j]>v);

if(i<j)
{
temp=a[i];
a[i]=a[j];
a[j]=temp;
}
    }while(i<j);
    a[l]=a[j];
    a[j]=v;
    return(j);
}

 void mergesort(int a[] ,int i , int j)
   {
int mid;
if(i<j)
{ mid=(i+j)/2;
  mergesort(a,i,mid);    //left recursion
  mergesort(a,mid+1,j);  //right recursion
  merge(a,i,mid,mid+1,j); //meging of two sorted sub-arrays
}
    }


void merge(int a[],int i1, int j1, int i2, int j2)
  {
     int temp[50];//array used for merging
     int i,j,k;
     i=i1;//beginning of the first list
     j=i2;//beginning of the second list
     k=0;
     while(i<=j1 && j <=j2) //while elemnts in both lists
      {
if(a[i]<a[j])
  temp[k++]=a[i++];
else
  temp[k++]=a[j++];
      }
    while(i<=j1)//copy remaining elements of the first list
       temp[k++]=a[i++];
    while(j<=j2)//copy remaining elements of the second list
       temp[k++]=a[j++];
  //Transfer elemnts from temp[] back to a[]
    for(i=i1,j=0;i<=j2;i++,j++)
       a[i]=temp[j];
  }


OUTPUT:-



1)Quick Sort
2)Merge Sort
3)Quit
Enter your choice : 1

Enter no of elements :4

Enter array elements :23 6 89 5

Sorted array is :5  6  23  89
1)Quick Sort
2)Merge Sort
3)Quit
Enter your choice : 2

Enter no of elements :4

Enter array elements :15 7 34 0

Sorted array is :0   7   15   34
1)Quick Sort
2)Merge Sort
3)Quit
Enter your choice : 3