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3 votes
0 answers
82 views

A strategy for number-guessing game

Let player A and player B are playing number-guessing game, which is: Player A draws one natural number $X$ in $1,2,\cdots,N$ at random. Player B guesses a number $Y$ in $1,2,\cdots, N$. Player A ...
2 votes
1 answer
132 views

Optimal strategy in number guessing game?

Consider the following game. Two players each create a passcode using the digits 0-9 four times with repetition allowed. The two take turns asking a yes or no question about the opponent's passcode. ...
1 vote
0 answers
95 views

Building a primitive programming language for solving math olympiad problem(TSTST 2015)

There was a 6th problem on USA TSTST 2015: A Nim-style game is defined as follows. Two positive integers $k$ and $n$ are specified, along with a finite set $S$ of $k$-tuples of integers (not ...
0 votes
0 answers
147 views

Guessing a secret number to maximize the result

You are given a set $A$ (all elements are different and positive) and a set $B$ (all elements are different and positive). Find a optimal number $x$ ( $0 < x \leqslant W$ where $W$ is a given ...
0 votes
1 answer
67 views

Find the longest subinterval of [0,1] with a finite number of queries

We have a number of intervals (either finite or infinite), not overlapping if not for their extreme points, which union is [0,1]. One of them is long at least 1/4, and all the others are not longer ...
1 vote
1 answer
63 views

Binary search on positive integer valued random variable

Let $X$ be a random variable taking values in $\{1,2,3,...\}$ and $\mathbb{E}(X)<+\infty$. $A$ has a realization of $X$. $B$ wants to guess what value does $A$ have and $B$ knows the distribution ...
7 votes
1 answer
830 views

Alice and Bob make all numbers to zero game

Alice and Bob are playing a number game in which they write $N$ positive integers. Then the players take turns, Alice took first turn. In a turn : A player selects one of the integers, divides it ...
2 votes
1 answer
66 views

Decomposing into sum game

There are $n$ numbers $a_1, a_2, ..., a_n$. Two players take turns. In each move, player chooses some number $a_i$ and writes it as a product of two numbers in any way he wants (so for exapmle $1470 = ...
4 votes
1 answer
679 views

Knight movement on chess field

I had this task in programming competition: There are two knights, which are $(p_1,q_1)$ and $(p_2, q_2)$. $(p,q)$ knight is figure, with p(q)-length first step, and q(p)-length second step in ...
-1 votes
1 answer
373 views

Finding winner of flipping game

Alice and Bob play a game with N non-negative integers. Players take successive turns, and in each turn, they are allowed to flip active bits from any of the integers in the list. That is, they ...
0 votes
1 answer
2k views

Number of ways to win chocolate game

Alice and Bob are playing a game. They have N containers each having one or more chocolates. Containers are numbered from 1 to N, where ith container has A[i] number of chocolates. The game goes like ...
1 vote
2 answers
739 views

Game of cards and GCD

Alice and Bob play the game. The rules are as follows: Initially, there are n cards on the table, each card has a positive integer written on it. At the beginning Alice writes down the number 0 on ...
1 vote
1 answer
220 views

Game Of Strings

There are two strings A and B. Initially, some strings A’ and B’ are written on the sheet of paper. A’ is always a substring of A and B’ is always a substring of B. A move consists of appending a ...
3 votes
1 answer
224 views

Play with pairs of numbers

Two players are playing a game. The game is played on a sequence of positive integer pairs. The players make their moves alternatively. During his move the player chooses a pair and decreases the ...
38 votes
1 answer
3k views

Is War necessarily finite?

War is an cardgame played by children and drunk college students which involves no strategic choices on either side. The outcome is determined by the dealing of the cards. These are the rules. A ...

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