public WhiteElephantElf(int gifts, int position, WhiteElephantElf next, WhiteElephantElf previous)
{
Gifts = gifts;
Position = position;
Next = next;
Previous = previous;
}
public int AcrossGetPositionWithAllTheGifts(int numberOfElves)
{
WhiteElephantElf firstElf = new WhiteElephantElf(1, 1, null, null);
WhiteElephantElf elf = firstElf;
WhiteElephantElf floatingTarget = null;
int floatingTargetIndex = PositionAcrossCircle(numberOfElves, 1);
// Build the ring
for (int i = 2; i <= numberOfElves; i++)
{
WhiteElephantElf nextElf = new WhiteElephantElf(1, i, null, elf);
elf.Next = nextElf;
elf = nextElf;
// Halfway across, get our target
if (i == floatingTargetIndex)
{
floatingTarget = elf;
}
}
// Complete last connection
elf.Next = firstElf;
firstElf.Previous = elf;
// Begin process of stealing
int count = numberOfElves;
WhiteElephantElf activeElf = firstElf;
while (activeElf.Next != activeElf)
{
activeElf.Gifts += floatingTarget.Gifts;
// Removes the target from circle
floatingTarget.Gifts = 0;
floatingTarget.Previous.Next = floatingTarget.Next;
floatingTarget.Next.Previous = floatingTarget.Previous;
// Determine new target
if (count % 2 == 1)
{
// If odd, then go forward 2
floatingTarget = floatingTarget.Next.Next;
}
else
{
// If even, only go forward 1
floatingTarget = floatingTarget.Next;
}
// Now move to elf on left
activeElf = activeElf.Next;
count--;
}
return(activeElf.Position);
}
public int GetPositionWithAllTheGifts(int numberOfElves)
{
WhiteElephantElf firstElf = new WhiteElephantElf(1, 1, null, null);
WhiteElephantElf elf = firstElf;
WhiteElephantElf floatingTarget = null;
// Build the ring
for (int i = 2; i <= numberOfElves; i++)
{
WhiteElephantElf nextElf = new WhiteElephantElf(1, i, null, elf);
elf.Next = nextElf;
elf = nextElf;
}
// Complete last connection
elf.Next = firstElf;
firstElf.Previous = elf;
floatingTarget = firstElf.Next;
// Begin process of stealing
WhiteElephantElf activeElf = firstElf;
while (activeElf.Next != activeElf)
{
activeElf.Gifts += floatingTarget.Gifts;
// Removes the target from circle
floatingTarget.Gifts = 0;
floatingTarget.Previous.Next = floatingTarget.Next;
floatingTarget.Next.Previous = floatingTarget.Previous;
// Determine new target
floatingTarget = floatingTarget.Next.Next;
// Now move to elf on left
activeElf = activeElf.Next;
}
return(activeElf.Position);
}
