// Merges two subarrays of arr[].
// First subarray is arr[l..m]
// Second subarray is arr[m+1..r]
void merge(int arr[], int l, int m, int r)
{
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 (int i = 0; i < n1; i++)
L[i] = arr[l + i];
for (int j = 0; j < n2; j++)
R[j] = arr[m + 1 + j];
// Merge the temp arrays back into arr[l..r]
// Initial index of first subarray
int i = 0;
// Initial index of second subarray
int j = 0;
// Initial index of merged subarray
int k = l;
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){
return;//returns recursively
}
int m =l+ (r-l)/2;
mergeSort(arr,l,m);
mergeSort(arr,m+1,r);
merge(arr,l,m,r);
}
