Find Common Elements Across Multiple Lists Using Sets

# Example 1: Finding common elements in three lists
list1 = [1, 2, 3, 4, 5]
list2 = [3, 4, 5, 6, 7]
list3 = [5, 6, 7, 8, 9]

# Convert lists to sets for efficient intersection
set1 = set(list1)
set2 = set(list2)
set3 = set(list3)

common_elements = set1.intersection(set2, set3)
print(f"Common elements across list1, list2, list3: {sorted(list(common_elements))}")
# Expected: [5]

# Example 2: Finding common words in multiple sentences
sentence1_words = "The quick brown fox jumps over the lazy dog".split()
sentence2_words = "A quick brown cat runs under the table".split()
sentence3_words = "The quick red fox barks loudly".split()

common_words = set(sentence1_words).intersection(set(sentence2_words), set(sentence3_words))
print(f"
Common words across sentences: {sorted(list(common_words))}")
# Expected: ['brown', 'quick', 'the'] (case-sensitive)

# Example 3: Generalizing for an arbitrary number of lists
all_lists = [
    [10, 20, 30, 40],
    [20, 30, 50, 60],
    [30, 40, 50, 70],
    [30, 80, 90]
]

# Start with the set of the first list, then intersect with the rest
if all_lists:
    common_across_all = set(all_lists[0])
    for lst in all_lists[1:]:
        common_across_all = common_across_all.intersection(set(lst))
    print(f"
Common elements across all lists: {sorted(list(common_across_all))}")
else:
    print("
No lists provided.")
# Expected: [30]