S2Q2 · First Top Performer by Average

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Type: Full I/O problem

Core idea: accumulate scores per student, compute averages, find the highest with first-appearance tie-breaking.

n = int(input())
scores   = {}
order    = []

for _ in range(n):
    name, score = input().split(",")
    score = int(score)
    if name not in scores:
        scores[name] = []
        order.append(name)
    scores[name].append(score)

best = max(order, key=lambda name: sum(scores[name]) / len(scores[name]))
print(best)

Key rules: - order list preserves first-appearance order - scores dict maps name → list of scores - max(order, key=lambda ...) - ties kept to first appearance since max only updates on strictly greater

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Problem Statement

Problem (I/O type)

Read n name,score records. Compute average per student. Print the name of the student with the highest average. Ties → first to appear in input.

Example:

Input

5
Alice,80
Bob,90
Alice,100
Bob,70
Carol,95

Output

Carol

Averages: Alice = (80+100)/2 = 90.0, Bob = (90+70)/2 = 80.0, Carol = 95/1 = 95.0 → Carol wins.

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Tracing the example

Name	Scores	Average
Alice	[80, 100]	90.0
Bob	[90, 70]	80.0
Carol	[95]	95.0 ← highest

First-appearance order: Alice (line 1), Bob (line 2), Carol (line 5)

max(order, key=avg) → Carol (95.0) ✓

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Solution approaches

PythonicUsing defaultdictExplanatoryUsing lambda + Counter

n = int(input())
scores = {}
order  = []

for _ in range(n):
    name, score = input().split(",")
    if name not in scores:
        scores[name] = []
        order.append(name)
    scores[name].append(int(score))

avg = lambda name: sum(scores[name]) / len(scores[name])
print(max(order, key=avg))

from collections import defaultdict

n = int(input())
scores = defaultdict(list)
order  = []

for _ in range(n):
    name, score = input().split(",")
    if name not in scores:
        order.append(name)
    scores[name].append(int(score))

print(max(order, key=lambda name: sum(scores[name]) / len(scores[name])))

defaultdict(list) auto-initialises empty lists. The if name not in scores check still works for tracking first appearance in order.

n = int(input())
scores = {}
order  = []

for _ in range(n):
    line  = input()
    name, score_str = line.split(",")
    score = int(score_str)
    if name not in scores:
        scores[name] = []
        order.append(name)
    scores[name].append(score)

# Compute averages and find best
best_name = order[0]
best_avg  = sum(scores[order[0]]) / len(scores[order[0]])

for name in order[1:]:
    avg = sum(scores[name]) / len(scores[name])
    if avg > best_avg:
        best_avg  = avg
        best_name = name

print(best_name)

from collections import defaultdict

n = int(input())
scores = defaultdict(list)
order  = []

lines = [input().split(",") for _ in range(n)]
for name, score in lines:
    if name not in scores:
        order.append(name)
    scores[name].append(int(score))

avg = lambda name: sum(scores[name]) / len(scores[name])
print(max(order, key=avg))

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Key takeaways

01

Separate order tracking from score accumulation

Use order list for first-appearance order and scores dict for the actual values. The list preserves insertion order; the dict provides O(1) lookup.

02

max(order, key=avg) preserves first on tie

max() iterates in the given order and only updates when it finds a strictly greater value. Iterating over order (first-appearance order) means ties keep the student who appeared first.

03

sum / len for running average

Store all scores in a list and compute sum/len at the end - simpler than maintaining a running average. For this problem size, the extra memory is negligible.