//Standard mergesort algorithm, sort left, sort right, merge.
void _mergeSort(vector<int> *arr, int start, int end)
{
if(start < end)
{
int mid = (end + start) / 2;
_mergeSort(arr, start, mid);
_mergeSort(arr, mid + 1, end);
merge(arr, start, mid, end);
}
}
long long _mergeSort(long long arr[], long long temp[], long long left, long long right)
{
long long mid, inv_count = 0;
if (right > left)
{
mid = (right + left)/2;
inv_count = _mergeSort(arr, temp, left, mid);
inv_count += _mergeSort(arr, temp, mid+1, right);
inv_count += merge(arr, temp, left, mid+1, right);
}
return inv_count;
}
long long int _mergeSort(int arr[], int temp[], int left, int right)
{
long long int mid, inv_count = 0;
if (right > left)
{
mid = (right + left)/2;
inv_count = _mergeSort(arr, temp, left, mid);
inv_count += _mergeSort(arr, temp, mid+1, right);
inv_count += merge(arr, temp, left, mid+1, right);
}
return inv_count;
}
/* An auxiliary recursive function that sorts the input array and returns the number of inversions
in the array. */
int _mergeSort(int arr[], int temp[], int left, int right)
{
int mid, inv_count = 0;
if (right > left)
{ /* Divide the array into two parts and call _mergeSortAndCountInv() for each of the parts */
mid = (right + left)/2;
/* Inversion count will be sum of inversions in left-part, right-part and number of inversions
in merging */
inv_count = _mergeSort(arr, temp, left, mid);
inv_count += _mergeSort(arr, temp, mid + 1, right);
inv_count += merge(arr, temp, left, mid + 1, right); /*Merge the two parts*/
}
return inv_count;
}
/* This function sorts the input array and returns the
number of inversions in the array */
int mergeSort(int arr[], int array_size)
{
//将字符串复制
int *temp = (int *)malloc(sizeof(int)*array_size);
//归并排序
return _mergeSort(arr, temp, 0, array_size - 1);
}
/* This function sorts the input array and returns the
number of inversions in the array */
int mergeSort(int arr[], int array_size)
{
int *temp = (int *)malloc(sizeof(int)*array_size);
return _mergeSort(arr, temp, 0, array_size - 1);
}
long long mergeSort(long long arr[], long long array_size)
{
long long *temp = (long long *)malloc(sizeof(long long)*array_size);
return _mergeSort(arr, temp, 0, array_size - 1);
}
void mergeSort(vector<int> *arr)
{
_mergeSort(arr,0,(*arr).size()-1);
}