Limit on the number of NPCs - unity3d

Question

Such an idea, for which I don't even have any ideas how to do it right. In general, the thought is:
There are, say, three NPCs on the stage (Conditionally), and there is also one building (Conditionally). Each NPC has its own task, but I do not know how to take an NPC who does not have a task and send one NPC to work in the building, and not several at once. Namely, each NPC has work statuses, and there is also a status 0, meaning that the NPC is not busy, there may be several such "free" ones, and if one is assigned the status of work - go to the building, then everyone who has this status will go, but how can we make sure that only one free NPC is taken and sent there?
I know the question is as incomprehensible and terrible as possible, but maybe someone will understand...

Answer 1

I made, so, to begin with, the code:
File WorkingPlace:
public static bool SignalFreeNPCPoint = false;
public static int WorkingPlaceNPC = 0;
public void ProductBoardNPC()
{
SignalFreeNPCPoint = true;
WorkingPlaceNPC += 1;
}
public void ProductBoard_Stop()
{
WorkingPlaceNPC -= 1;
SignalFreeNPCPoint = true;
}
This "ProductBoardNPC()" and "ProductBoard_Stop()" method's for button in Unity.
File NPCSctipt:
public List<GameObject> ListGM = new List<GameObject>();
public int TaskNumber = 0;
void Update()
{
TaskManager();
LogicNPC();
}
private void TaskManager()
{
switch (TaskNumber)
{
case 0:
//You code
break;
case 1:
ListGM.Remove(gameObject);
break;
case 2:
ListGM.Remove(gameObject);
break;
case 3:
ListGM.Remove(gameObject);
break;
case 4:
ListGM.Remove(gameObject);
break;
}
}
private void LogicNPC()
{
if (WorkingPlace.SignalFreeNPCPoint == true)
{
if (TaskNumber == 0 & WorkingPlace.WorkingPlaceNPC == 1)
{
ListGM.Add(gameObject);
TaskNumber = 4;
}
if (TaskNumber == 4 & WorkingPlace.WorkingPlaceNPC == 0)
{
TaskNumber = 0;
}
WorkingPlace.SignalFreeNPCPoint = false;
}
}
How the code works:
When you click on the button, an NPC with the status 0 is searched, the last NPC with this status is taken and entered into the array, after which it is given a different status to perform "work", after which it is removed from the array to make room for another NPC.
In this case, the array is a buffer and is simply necessary. If you have better ideas than mine, I will be happy to listen)
The implementation is a clean bike made of crutches, but it works flawlessly. Yes, about FPS drawdowns, it doesn't seem to load the system much, if there are drawdowns, then write what to fix.