"Same" means, here, that the elements in b are the elements in a squared, regardless of the order.

9 is squared 3, 9 is squared 3, 4 is squared 2

You can use the '%' operator. Look my solution

What is the g sequence? I don't understand it

Instead of

cashOnHand[person]++;
cashOnHand[50]++;
cashOnHand[100]++;```

you can use only 

```cashOnHand[person]++;``` 


at the beginning or at the end in the block of the for loop.
If you did it, you would be able to remove the first if block

Instead of
cash[25] ++;
cash[50] ++;
cash[100] ++;

you can use
cash[people]++; at the begining or at the end in the for block

If you did it, you would be able to remove the first case in the switch

It looks like my own solution!

But you should check reg[25] >= 3 not reg[25] == 3
and
reg[50] >= 1 && reg[25] >= 1

also you have a string
if (reg[25] == 3) reg[50] += -3;

you check reg[25], but act on reg[50] !

Your solution failed on this test

Assert.AreEqual("YES", Line.Tickets(peopleInLine));```

On each iteration you find a change in a list. The complexity is O(n^2)
Dictionary should be better.
Check my solution.

You can compare chars e.g. 'a' < 'z';