I have no clue how to answer this question. This is 2002 Putnam examination question B-4.
B4 An integer $n$, unknown to you, has been randomly chosen in the interval $[1,2002]$ with uniform probability. Your objective is to select $n$ in an odd number of guesses. After each incorrect guess, you are informed whether $n$ is higher or lower, and you must guess an integer on your next turn among the numbers that are still feasibly correct. Show that you have a strategy so that the chance of winning is greater than $\frac23$.
Frankly speaking, I didn't understand the phrase 'an odd number of guesses'.
For example, if n is 1000, and I guess 10 in my 1st attempt, then I will be informed that n is higher than that number.
In the 2nd attempt, if I guess 1000, then it would be a correct guess. That means I correctly guessed $n=1000$ in an even number of guesses.
Is this understanding correct?
I have a solution to this problem but I didn't understand it. There are 4 points given in the solution. But as the problem is unclear to me, solution is obviously unclear to me. The solution is as follows:-
If any member understands the given solution correctly, may reply with the correct explanations of all the 4 points.