S2Q2 · Movie List Watch Time and Unique Movies

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Type: Full I/O problem

Core idea: parse each list's two lines, accumulate total watch time per list and a global set of unique movies, then print.

n = int(input())
totals  = []
all_movies = set()

for _ in range(n):
    list_line  = input()
    time_line  = input()
    list_name, movies_str = list_line.split(";")
    movies = movies_str.split(",")
    times  = list(map(int, time_line.split(",")))
    totals.append((list_name, sum(times)))
    all_movies.update(movies)

for name, total in totals:
    print(f"{name}: {total}")

print("Unique movies across all lists:", ", ".join(sorted(all_movies)))

Key rules: - First line of each entry: ListName;Movie1,Movie2,... - Second line: t1,t2,... (corresponding watch times) - Print totals in input order - Print unique movies sorted lexicographically, comma-and-space separated

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Problem Statement

Problem (I/O type)

Read n movie lists, each with movies and watch times. Print total watch time per list, then all unique movie names sorted alphabetically.

Example:

Input

3
Watchlist1;Inception,Dunkirk,Tenet
120,106,150
Watchlist2;Interstellar,Tenet
169,150
Watchlist3;Inception,Joker
120,122

Output

Watchlist1: 376
Watchlist2: 319
Watchlist3: 242
Unique movies across all lists: Dunkirk, Inception, Interstellar, Joker, Tenet

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Understanding the input format

Each list entry spans two lines:

Watchlist1;Inception,Dunkirk,Tenet    ← ListName;Movie1,Movie2,...
120,106,150                           ← t1,t2,... (same order as movies)

Parsing:

list_line.split(";")     →  ["Watchlist1", "Inception,Dunkirk,Tenet"]
movies_str.split(",")    →  ["Inception", "Dunkirk", "Tenet"]
time_line.split(",")     →  ["120", "106", "150"]
sum(map(int, ...))       →  376

Tenet appears in both Watchlist1 and Watchlist2 - the set deduplicates automatically.

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Tracing the example

List	Movies	Times	Total	New unique movies
Watchlist1	Inception, Dunkirk, Tenet	120, 106, 150	376	Inception, Dunkirk, Tenet
Watchlist2	Interstellar, Tenet	169, 150	319	Interstellar (Tenet already in set)
Watchlist3	Inception, Joker	120, 122	242	Joker (Inception already in set)

Unique movies sorted: Dunkirk, Inception, Interstellar, Joker, Tenet ✓

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Solution approaches

PythonicExplanatoryUsing lambda + map

n = int(input())
totals     = []
all_movies = set()

for _ in range(n):
    list_name, movies_str = input().split(";")
    times = list(map(int, input().split(",")))
    movies = movies_str.split(",")
    totals.append((list_name, sum(times)))
    all_movies.update(movies)

for name, total in totals:
    print(f"{name}: {total}")

print("Unique movies across all lists:", ", ".join(sorted(all_movies)))

n = int(input())
totals     = []
all_movies = set()

for _ in range(n):
    # Parse list line
    list_line = input()
    list_name, movies_str = list_line.split(";")
    movies = movies_str.split(",")

    # Parse time line
    time_line = input()
    times = [int(t) for t in time_line.split(",")]

    # Accumulate
    total = sum(times)
    totals.append((list_name, total))
    for movie in movies:
        all_movies.add(movie)

# Output totals
for name, total in totals:
    print(f"{name}: {total}")

# Output unique movies
unique_sorted = sorted(all_movies)
print("Unique movies across all lists: " + ", ".join(unique_sorted))

n = int(input())
entries = []
for _ in range(n):
    name, movies_str = input().split(";")
    times = list(map(int, input().split(",")))
    entries.append((name, movies_str.split(","), sum(times)))

list(map(lambda e: print(f"{e[0]}: {e[2]}"), entries))

all_movies = sorted(set(
    movie for _, movies, _ in entries for movie in movies
))
print("Unique movies across all lists:", ", ".join(all_movies))

Collects all entries first, then uses map(lambda ...) for printing totals. The nested generator flattens all movie lists into one set for deduplication.

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Key takeaways

01

set.update() for batch deduplication

all_movies.update(movies) adds all movies from the current list to the set at once - automatically deduplicating. Equivalent to a loop of add() calls but cleaner.

02

Store totals in order before printing

Sets are unordered - they can't track per-list totals. Store (name, total) tuples in a list to preserve input order for the first output block, then use the set only for the unique movies.

03

", ".join(sorted(set)) for sorted unique output

sorted() returns a sorted list from any iterable including sets. ", ".join(...) formats it as comma-and-space separated. The two together handle both requirements in one line.