"""
[10, 20, 30, 40, 50]
[15, 20, 35, 50, 76, 190]

idx_a 2
idx_b 2

--> [20, 50]

[10, 20]
[]

--> []
"""

def intersect_lists(list_a, list_b):
    idx_a, idx_b = 0, 0
    result = []
    while idx_a < len(list_a) and idx_b < len(list_b):
        num_a, num_b = list_a[idx_a], list_b[idx_b]

        if num_a == num_b:
            result.append(num_a)
            idx_a += 1
            idx_b += 1
        elif num_a < num_b:
            idx_a += 1
        else:
            idx_b += 1

    return result

print(intersect_lists([10, 20, 30, 40, 50], [15, 20, 35, 50, 76, 190]))
print(intersect_lists([10, 20], []))