common strings in two lists of strings in Python

Question

This question already has answers here: question from:https://stackoverflow.com/questions/65936256/common-strings-in-two-lists-of-strings-in-python

Answer 1

since the value in a are unique, so you can create a dict, in O(n), to access and check that element in O(1).

Iterate through b and check each element of b with dict in O(1), it will save time then using set operation and also include if there are same multiple same element present in b and in a also

a = ['ab','ac','ad', 'aba','abc'] # n = 10000 of unique strings
b = ['ab', 'ac', 'ab', 'kk']               # m = 100 have duplicates
c = []


a_dic = {i:1 for i in a}
sol = []

for i in b:
    if a_dic.get(i, None):
        sol.append(i)