Cows and Bulls

For all those who wear the hat of a six year old while reading this blog, PREPARE TO UPGRADE! This is a cerebral game, contributed by Shyam.

He says, "The whole concept of the game 'cows and bulls' is hitting the bull's eye - hence the name."

Will explain the rest of the game using a scenario. Two players needed, and two players you shall have - call them Veeru and Jai.

Veeru writes a 4 digit secret number on a piece of paper, the Jai starts guessing the number. Veeru has to follow one simple rule while making up the 4 digit number - No repeating any digit. As in, numbers like 1918, 2020, 1124, 6188 - NOT ALLOWED.

So Veeru writes 1947 on the paper. Jai has NO clue what that number is for the first 2-3 chances. Jai tries a random guess - 2468. Writes it on paper and shows Veeru.

Veeru says, "1 cow, 0 bulls".

1 cow because on correct digit i.e., '4' appears.
0 bulls because, there are NO numbers which are at the same spot as Veeru's number(1947).

From this first clue, Jai writes his next number - again random - 1357

Veeru says, "0 cows, 2 bulls".

Jai hit 2 bulls because, "1" and "7" are at the right spot.

Then, Jai takes a third guess: - 1349
Wrong guess, he thinks "1" and "3" are the bulls. And this is how the rest of the game went:

1349 --- 1 cow, 2 bulls
1392 --- 1 cow, 1 bull (Jai: 'Either 3 is a bull OR 1 is a bull, not both')
1952 --- 0 cows, 2 bulls (Jai: 'I thought from my old 1357 guess, '5' is there')
1054 --- 1 cow, 1 bull
1954 --- 1 cow, 2 bulls
1974 --- 2 cows, 2 bulls ( Jai: 'Now I got ALL four digits, 2 in correct place, 2 misplaced')
1947 --- 4 BULLS !!!

And finally, an end-note by Shyam on this game:
This game requires analysis of each guess and discarding numbers in the right fashion. Usually, average is 6-7 guesses. If beyond this, something is really wrong - either the guesser is getting things wrong OR, the one who says 'cows and bulls' is messing things up.

ENJOY!