public List <int> countSmaller(int[] nums)
{
NumberIndex[] cnums = new NumberIndex[nums.Length];
for (int i = 0; i < nums.Length; i++)
{
cnums[i] = new NumberIndex(nums[i], i);
}
int[] smaller = new int[nums.Length];
cnums = sort(cnums, smaller);
List <int> res = new List <int>();
foreach (int i in smaller)
{
res.Add(i);
}
return(res);
}
private NumberIndex[] sort(NumberIndex[] nums, int[] smaller)
{
int half = nums.Length / 2;
if (half > 0)
{
int i = 0;
NumberIndex[] rightPart = new NumberIndex[nums.Length - half];
NumberIndex[] leftPart = new NumberIndex[half];
for (i = 0; i < leftPart.Length; i++)
{
leftPart[i] = new NumberIndex(nums[i]);
}
for (i = 0; i < rightPart.Length; i++)
{
rightPart[i] = new NumberIndex(nums[half + i]);
}
NumberIndex[] left = sort(leftPart, smaller), right = sort(
rightPart, smaller);
int m = left.Length, n = right.Length;
i = 0;
int j = 0;
while (i < m || j < n)
{
if (j == n || i < m && left[i].number <= right[j].number)
{
nums[i + j] = left[i];
smaller[left[i].index] += j;
i++;
}
else
{
nums[i + j] = right[j];
j++;
}
}
}
return(nums);
}
public NumberIndex(NumberIndex another)
{
this.number = another.number;
this.index = another.index;
}