public T GetRunningSum(int startIndex, int endIndex)
{
if ((startIndex < 0) || (startIndex >= this.Count))
{
throw new ArgumentOutOfRangeException("startIndex", startIndex, "The index must be greater or equal to zero and lesser than the collection Count.");
}
if ((endIndex < 0) || (endIndex >= this.Count))
{
throw new ArgumentOutOfRangeException("endIndex", endIndex, "The index must be greater or equal to zero and lesser than the collection Count.");
}
if (startIndex > endIndex)
{
throw new ArgumentException("The start index must be lesser than or equal to the end index.", "startIndex");
}
var x = FenwickTree <T> .ConvertIndex(endIndex);
var y = FenwickTree <T> .ConvertIndex(startIndex - 1);
var sum = default(T);
while (x > y)
{
sum = this.Add(sum, m_collection[x]);
x -= FenwickTree <T> .FindLastDigit(x);
}
while (y > x)
{
sum = this.Substract(sum, m_collection[y]);
y -= FenwickTree <T> .FindLastDigit(y);
}
return(sum);
}
public T this[int index]
{
get
{
return(this.GetRunningSum(index, index));
}
set
{
var current = this[index];
if (object.Equals(current, value))
{
return;
}
var diff = this.Substract(value, current);
var x = FenwickTree <T> .ConvertIndex(index);
while (x < m_collection.Length)
{
m_collection[x] = this.Add(m_collection[x], diff);
x += FenwickTree <T> .FindLastDigit(x);
}
}
}