from typing import List, TypeVar
T = TypeVar("T")
def find_list_intersection(list1: List[T], list2: List[T]) -> List[T]:
"""Finds the unique intersection of two lists (values that exist in both).
Maintains order based on the first occurrence in the first list.
Time Complexity: O(N + M) where N and M are the lengths of the lists.
Space Complexity: O(min(N, M)) auxiliary space for the set lookups.
Args:
list1: The first list sequence.
list2: The second list sequence.
Returns:
A list of unique elements present in both input lists.
"""
# Convert the second list to a set for O(1) average lookup time
lookup_set = set(list2)
# Use a set to track already matched items to guarantee uniqueness
seen = set()
result = []
# Iterate through list1 to preserve initial ordering of matches
for item in list1:
if item in lookup_set and item not in seen:
result.append(item)
seen.add(item)
return result
# --- Usage Example ---
if __name__ == "__main__":
lst1 = [5, 7, 1, 1, 3, 0, 6, 2]
lst2 = [2, 8, 8, 6, 9, 3, 3, 4, 4]
intersection = find_list_intersection(lst1, lst2)
print(f"List 1: {lst1}")
print(f"List 2: {lst2}")
print(f"Intersection: {intersection}")
'''
run:
List 1: [5, 7, 1, 1, 3, 0, 6, 2]
List 2: [2, 8, 8, 6, 9, 3, 3, 4, 4]
Intersection: [3, 6, 2]
'''
