Lasa cartea din mana si se indreapta spre raionul de jocuri. Aici vede pe perete un poster mare, cu o configuratie a unui joc pe care il stie din copilarie: X si O.

A. X si O (10%)

Jocul X si O (sau Tic-Tac-Toe) se joaca pe o tabla de 3x3 asftel:

1. Fiecare dintre cei 2 jucatori isi plaseaza semnul (X sau 0) intr-un patrat liber;
2. Primul jucator care completeaza o linie, coloana sau diagonal cu semnul sau (X sau 0) castiga;
3. Un jucator va plasa semnul sau intotdeauna pe o linie, coloana sau diagonala care contine deja 2 semne ale sale (pentru a castiga), sau pe o linie, coloana sau diagonala care contine deja 2 semne ale jucatorului advers (pentru a il impiedica pe celalalt sa castige, in caz ca el nu poate castiga).

In configuratia de mai jos lipseste doar o singura mutare. Cine castiga jocul (X sau 0)? Explicati rationamentul.

Sursa: George J.Summers , "The great book of mind teasers&mind puzzles”

He puts the book down and heads to the games section. Here he sees a large poster hanging on the wall, with a configuration of a game he knows from childhood: X and O.

A. X si O (10%)

The game of X si O (or Tic-Tac-Toe) is played on a 3x3 square table:

1. Each of the 2 players, in turn, places his / her mark (X or 0) in an empty square;
2. The player who first gets 3 of his / her marks in a horizontal, vertical or diagonal line wins;
3. A player will always place his / her mark in a line that already contains 2 of his / her marks (to win), or in a line that already contains 2 marks of the opponent (to prevent the other winning, if he / she cannot win).

Only the last mark to be placed in the game is not given. Who wins the game (X sau 0)? Explain why.

Source: George J.Summers , "The great book of mind teasers&mind puzzles”