I broke this project into 2 basic parts, an atlas (map is a reserved word), and a 'battle'. The atlas is a map of city names onto structs. Each struct has 4 pointers, N S E and W, and they point to cities in their respective directions. The 'battle' is a slice containing pointers to warzone structs. Each warzone contains the ID of any aliens in it and a pointer to the city being attacked. Warzones are updated every time an alien enters a city, and the atlas is updated every time a city is destroyed.
Here is a really simple controller function you can use to simulate the attack. Wherever this is being invoked from needs to have the input file.
package main
import "github.com/jamesonev/alien"
func main() {
alien.Attack()
}
You can run this with go run main.go 5, with however many aliens you want. You also have the option to specify an input file for the program as the final argument in the command line. If no file is specified, the program will look for a file named input.txt in the current directory.
At the end, Attack prints the current atlas including any roads between cities. It also does a check of all remaining cities for aliens and prints out the location and number of any found, which is helpful for checking the correctness of the implementation
This is my first Go project, and so it had quite a steep learning curve. Conceptually, I'm used to separating my code into .c/.h files and linking them in a makefile, so transitioning into thinking in terms of packages was challenging. You can see that I tried to use good cohesion/coupling practices, like how atlas.go has no knowledge of the battle. However, figuring out the most elegant way to do that in a package was challenging.
One thing that may appear to be a bug is that if 2 aliens are in adjacent cities that are only linked to each other, they will constantly switch cities without ever meeting to fight. This may appear to be a bug, but its a result of implementing the behavior described in the spec.