public T ConcatTo(int i)
{
var r = _monoid.Unit;
for (i++; i > 0; i -= i & -i)
{
r = _monoid.Append(r, _tree[i]);
}
return(r);
}
public FenwickTree(IEnumerable <T> collection, Monoid <T> monoid)
{
var count = collection.Count();
_monoid = monoid;
_tree = new T[count + 1];
collection.ForEach((x, i) => { _tree[i + 1] = x; });
for (var i = 1; i < count; i++)
{
var j = i + (i & -i);
if (j < count)
{
_tree[j] = monoid.Append(_tree[j], _tree[i]);
}
}
}
public SegmentTree(IList <T> collection, Monoid <T> monoid)
{
if (collection.Count > (int.MaxValue >> 1) + 1)
{
throw new ArgumentException();
}
_size = 1;
while (_size < collection.Count)
{
_size <<= 1;
}
_tree = new T[_size << 1];
for (var i = 0; i < _size; i++)
{
_tree[i + _size] = i < collection.Count ? collection[i] : monoid.Unit;
}
for (var i = _size - 1; i > 0; i--)
{
_tree[i] = monoid.Append(_tree[i << 1], _tree[(i << 1) + 1]);
}
this.Monoid = monoid;
this.Length = collection.Count;
}
