# 100 Cards with numbers in a room [duplicate]

The scenario is like this:

There's a room, inside the room there are 100 cards with numbers [1,100] on them (No duplications), the cards are ordered randomly.

Two persons stand outside the room, They can decide on a tactic before the following:

• One person enters the room, he can see the order, he can make one switch between places of two numbers. (e.g: (3,1,2) ---switch 3 and 1---> (1,3,2)).
• After the switch (Or not switching) the person flips the cards and exits the room. (Other than the switch, the person does not change the order)
• The second person enters the room, A number between [1,100] is called out of the void, he has 50 guesses to get that number.

A few notes:

• The cards are in a perfect line, you can't order them vertically or something like that.
• The cards are identical, There are no particular features for specific cards or something like that.
• You can't leave anything in the room (items / human parts / ...)
• The two persons have no idea about the number that will be called.
• A guess = Flips a particular card.
• This is not the same as the prisoners, Since the first person doesn't know about the number the second person is supposed to find.
• Isn't this the same as this one? puzzling.stackexchange.com/q/16/19989 Apr 10, 2017 at 7:35
• @Marius No, because that one has 100 people while this one has only 2. Apr 10, 2017 at 8:34
• @randal'thor But the case with 2 people is a subcase in that question. Apr 10, 2017 at 8:41
• You explain a scenario, but you put no actual question. What are we, as solvers, to do? Apr 10, 2017 at 15:41
• Possible duplicate of “How to beat Count Dracula”. Apr 10, 2017 at 16:34