March 22, 2006


The recent Sudoku fever made me rethink the brain itching site! here it is a very neat and good sudoku game, enjoy. BTW, if you don't yet know the game, the objective is to have all rows and columns and highlighted 3*3 squares have every digit from 1 to 9.

It will be great, if you share your records, in the comments section. BTW, if you don't know what Sudoku is take a look at here. Also Spectrum recently had a short article on sudoku solution. It is interesting to find an algorithm that can solve the puzzle in polynomial time, or prove that it is impossible to do so.

Posted by Shauheen at 12:45 AM | Comments (17)

May 16, 2004

سلول انفرادي

در يک کشور فرضي! صد نفر روزنامه نگار در سلولهاي انفرادي زنداني هستند.

سلول ها کاملا بسته هستند ( آکوستيک و بدون پنجره براي نور ). زندانبان هر روز يک نفر از زندانيان را به صورت تصادفي انتخاب کرده و به سالني مي برد. در سالن چراغي هست که زنداني مي تواند در طول روزي که در سالن به سر مي برد آن چراغ را روشن يا خاموش کند.

چراغ در روز نخست خاموش است. به هر زنداني امکان اين داده مي شود که اعتراف کند که هر نود و نه زنداني ديگر حداقل يک بار به سالن برده شده اند. اگر يک زنداني اين اعتراف را بنويسد و دروغ گفته باشد٬ تمام يکصد زنداني همان شب يا به طور تصادفي بر اثر کوبيدن سر خودشان به جسم سخت يا به علت خوردن داروي نظافت يا به هر دليلي که اصلا به من و شما مربوط نيست اندکي فوت خواهند کرد.

در حاليکه اگر صحت داشته باشد تمام زنداني ها فردا صبح آزاد مي شوند تا از کشورشان مهاجرانده شوند تا يک وبلاگ درست کنند و راه هاي حل اين معما را در زندانهاي ديگر هم بررسي کنند. پيش از روز نخست زندانيها را يک بار با هم به حياط زندان مي برند تا اگر مي خواهند از هم خداحافظي کنند!

زندانيها چه کنند؟

Posted by Shauheen at 05:40 PM | Comments (473)

May 08, 2004

5 pirates

This problem contributed by Bahram:

There are 5 pirates who steal 100 diamonds and they want to divide them. They decide to do so as follows:

They create a circle and choose a person by chance so that he assigns diamonds according to his wish. Nevertheless, to have a little more reasoning, they decide to add a second rule: once the division is made, everyone will vote if he is OK with this division or not. If the majority accept the division, then the division becomes final.
Otherwise, they kill the person who made the division, and the next pirate in the circle will do the division with the same rules.

The question is: what is an optimal strategy for the first person,
knowing that everyone would want to maximize his share and that everyone is excellent in logical deduction!

Another thing: when one makes the vote between 5, assuming that he himself votes O.K., 3 negative votes will be regarded as "NO". When one makes the vote between 4, still assuming that he votes O.K., 2 negative votes will be a "NO".

Posted by Shauheen at 10:37 PM | Comments (1551)