public int ReversePairs(int[] nums)
{
SortedSet <long> allNumbers = new SortedSet <long>();
foreach (int num in nums)
{
allNumbers.Add((long)num);
allNumbers.Add(2 * (long)num);
}
Dictionary <long, int> values = new Dictionary <long, int>();
int index = 0;
foreach (var num in allNumbers)
{
values.Add(num, index);
index++;
}
int res = 0;
BIT bit = new BIT(values.Count);
for (int i = 0; i < nums.Length; i++)
{
int left = values[(long)nums[i] * 2];
int right = values.Count - 1;
res += bit.Query(right + 1) - bit.Query(left + 1);
bit.Update(values[(long)nums[i]] + 1, 1);
}
return(res);
}
static void Main(string [] args)
{
int [] a = { 3, 6, 1, 7, 2, 8, 4, 9, 10 };
var bit = new BIT(a.Length);
bit.Build(a);
bit.Print();
Console.WriteLine(bit.Sum(a.Length - 1));
bit.Update(3, 2);
Console.WriteLine(bit.Sum(1, 3));
}
static void Main()
{
Console.WriteLine("I love you");
int [] arr = { 4, 6, 1, 8, 3, 2, 9, 0, 5, 7 };
var bit = new BIT(arr);
bit.Display();
Console.WriteLine();
for (int i = 0; i < arr.Length; i++)
{
Console.Write(bit.Sum(i) + " ");
}
bit.Update(10, 7);
Console.WriteLine();
for (int i = 0; i < arr.Length; i++)
{
Console.Write(bit.Sum(i) + " ");
}
Console.Write(bit.Sum(1) - bit.Sum(0));
}
