(here goes the answer) both algorithms you've implemented have similar time and space complexities.

1. get_item_from_list1 (Two Pointer Algorithm)

Time Complexity:

In the worst case, this algorithm checks every element in the list, resulting in a time complexity of O(n), where n is the length of the list. While it checks two elements per iteration (one from the left and one from the right), the asymptotic complexity remains O(n).

Space Complexity:

This algorithm uses constant extra space (for the indices and collection length), resulting in a space complexity of O(1).

2. get_item_from_list2 (Single Pointer Algorithm)

Time Complexity:

This algorithm also iterates through the list, leading to a worst-case time complexity of O(n).

Space Complexity:

Similar to the first algorithm, this one uses a constant amount of extra space, resulting in a space complexity of O(1).

So, both algorithms have the same theoretical time and space complexities. While the two-pointer algorithm may perform slightly better in practice due to checking two elements per iteration, this difference is insignificant in big-O notation.

If you're looking for a more efficient search method for sorted lists, consider using binary search. This method has a time complexity of O(log n), but it requires the list to be sorted beforehand.