Added Merge sort

[siddharthnarula]

#include
#include<conio.h>
#include<dos.h>
#include<time.h>
#include<stdlib.h>
#include<windows.h>
using namespace std;
void merge(int arr[], int l, int m, int r)
{
int i, j, k;
int n1 = m - l + 1;
int n2 = r - m;

/* create temp arrays */
int L[n1], R[n2];

/* Copy data to temp arrays L[] and R[] */
for (i = 0; i < n1; i++)
    L[i] = arr[l + i];
for (j = 0; j < n2; j++)
    R[j] = arr[m + 1+ j];

/* Merge the temp arrays back into arr[l..r]*/
i = 0; // Initial index of first subarray
j = 0; // Initial index of second subarray
k = l; // Initial index of merged subarray
while (i < n1 && j < n2)
{
    if (L[i] <= R[j])
    {
        arr[k] = L[i];
        i++;
    }
    else
    {
        arr[k] = R[j];
        j++;
    }
    k++;
}

/* Copy the remaining elements of L[], if there
   are any */
while (i < n1)
{
    arr[k] = L[i];
    i++;
    k++;
}

/* Copy the remaining elements of R[], if there
   are any */
while (j < n2)
{
    arr[k] = R[j];
    j++;
    k++;
}

}

/* l is for left index and r is right index of the
sub-array of arr to be sorted */
void mergeSort(int arr[], int l, int r)
{
if (l < r)
{ Sleep(1000);
// Same as (l+r)/2, but avoids overflow for
// large l and h
int m = l+(r-l)/2;

    // Sort first and second halves
    mergeSort(arr, l, m);
    mergeSort(arr, m+1, r);

    merge(arr, l, m, r);
}

}

void printArray(int arr[], int size)
{
int i;
for (i = 0; i < size; i++)
cout << arr[i] << " ";
cout << endl;
}
int main()
{
clock_t start,end;
int arr[100],n=25;
for(int i=0;i<n;i++)
{
arr[i] = (rand()%100+1);
cout << arr[i] << endl;
}
//int n = sizeof(arr)/sizeof(arr[0]);
start=clock();
mergeSort(arr,0,n);
end=clock();
cout<<"Sorted array: \n";
printArray(arr, n);
float t=(end-start)/CLK_TCK;
cout<<"\n Time Taken is"<<t;
return 0;
}