I have been searching for so long now for the title of a short-story I read in the late 1990s, I think. Possibly early 2000s. The plot goes along something like this. There is a boy, I think he may have just recently graduated from college. He starts to play a computer game. It is a war game that he has to program the correct amount of weapons to use to be able to win the war.
He becomes obsessed with the game as he just can't work out what the answer could be and he tries a multitude of numbers. I think he has a girlfriend that ends up walking out on him due to his obsession. His world falls apart around him because of the game (it may or may not actually be real but I could be confusing that with Ender's Game). It turns out that the correct answer is zero because there are (surprise surprise) no winners in war.
I thought this was a Stephen King short story but I have trawled through the list of every SK short story ever written and I cannot find it anything that even closely resembles this one. It's not the movie/book WarGame.