Synonym for 'arrive independently' at same solution
There are a number of articles online that call it simultaneous invention or simultaneous discovery:
This phenomenon of simultaneous discovery—what science historians call “multiples”—turns out to be extremely common.
Wikipedia calls it multiple discovery:
The concept of multiple discovery is the hypothesis that most scientific discoveries and inventions are made independently and more or less simultaneously by multiple scientists and inventors. The concept of multiple discovery opposes a traditional view—the "heroic theory" of invention and discovery.