Strategy notes

When it comes to strategy, I have noticed a couple of approaches.

One symbol at a time

The one color at a time guesses a row of the same symbol for all but one symbol. After you have done this you will know exactly how many of each symbol there is, but you won't know the order and guessing the order will take a couple of tries.

The obvious disadvantage to this approach is that it will require 6 guesses before you will even start trying to crack the code. The AI will rarely require more than 6 guesses therefore this is a method of making sure you are losing. It would have merit if there was no AI and you had many guesses to get it right.

Two symbols at a time

Improving on the one symbol at a time, this will only require 3 guesses, but it adds more uncertainty. Still as the previous iteration is a surefire way to lose this one might actually be worth a try.

Iterative what if

This approach can be combined with any strategy. First of make a guess, any guess. Then work up the list of guesses asking the following question: If this was the code, would this row have been scored like this? If the answer is yes do the same for all other rows. However if the answer is no, change your guess so that your new guess would have scored the current row the same score it did get. Keep working until your guess passes all checks.

Get lucky

The strategy favored by Nell in Advance Wars. Because allegedly luck is a skill.

With a 1 in quite a lot chance of randomly guessing the code, the viability of this strategy can be questioned. However with the amount of people in the world, sooner or later someone will get lucky. Said person will probably be feeling very sad that they wasted all their luck on Bulls and Cows instead of buying a lottery ticked, but that's life for you!