Execution flow diagram (call-stack) of recursive count-down
It would be better to add the method arguments in the diagram, for example:

printit(0) -- n=0, prints "0,", returns 0
printit(1) -- n=1, prints "0,", returns 0
printit(2) -- n=2, prints "1,", returns 1
main()


I don't think you need 4 drawings side by side for this, just one like this would be clear enough already.