Slice copy
Also written: path[:], slice
`path[:]` makes a new list with the same items. Backtracking saves it instead of `path`, because `path` is the one list that keeps changing and would end up empty.
Also written: path[:], slice
`path[:]` makes a new list with the same items. Backtracking saves it instead of `path`, because `path` is the one list that keeps changing and would end up empty.