← Computer Programming I

Problem 1: Sensor Data Aggregation

Problem Statement: You are working with a log file from a set of climate sensors. The log is represented as a list of tuples, where each tuple contains a (sensor_id, temperature). Each sensor may report multiple readings.

Your task is to write a function summarize_sensor_data that processes this list and returns a summary. The summary should be a list of tuples, where each tuple contains a unique sensor_id and its highest recorded temperature.

Requirements:

  1. The function must find the maximum temperature for each unique sensor ID.
  2. The final output list must be sorted alphabetically by sensor ID.
  3. If the input list of readings is empty, the function should return an empty list.

Test Cases: Case 1:

readings = [
	('SensorB', 25.4),
	('SensorA', 22.1),
	('SensorB', 26.1), # New max for SensorB
	('SensorC', 30.5),
	('SensorA', 21.9), # Lower than previous SensorA reading
	('SensorB', 25.9)
]
# Expected Output: [('SensorA', 22.1), ('SensorB', 26.1), ('SensorC', 30.5)]

Case 2:

readings_empty = []
# Expected Output: []
Problem 2: Top N Frequent Elements

Problem Statement: Write a function get_top_n_frequent(items, n) that takes a list of items and an integer n, and returns a list of the n most frequent items.

Requirements:

  1. The function should determine the frequency of each unique item in the items list.
  2. It should return a list containing the n items that appear most frequently.
  3. Tie-Breaking Rule: If two items have the same frequency, the one that comes first alphabetically or numerically should be ranked higher.
  4. The final returned list should be ordered from most frequent to least frequent.
  5. If the number of unique items is less than n, return all unique items, ordered by frequency.

Test Cases: Case 1:

votes = ['apple', 'orange', 'banana', 'apple', 'orange', 'apple', 'grape']
n = 2
# Frequencies: apple=3, orange=2, banana=1, grape=1
# Top 2 are 'apple' and 'orange'.
# Expected Output: ['apple', 'orange']

Case 2 (with tie-breaking):

words = ['code', 'sleep', 'eat', 'code', 'repeat', 'eat', 'code', 'sleep']
n = 3
# Frequencies: code=3, sleep=2, eat=2, repeat=1
# 'code' is #1. For #2, 'eat' and 'sleep' are tied. 'eat' comes before 'sleep' alphabetically.
# So the top 3 are 'code', 'eat', 'sleep'.
# Expected Output: ['code', 'eat', 'sleep']
Problem 3: Matrix Diagonal Sums

Problem Statement: Write a function sum_diagonals(matrix) that calculates the sum of the elements on the two main diagonals of a square matrix (an n x n grid).

Definitions:

  • The primary diagonal consists of elements from the top-left to the bottom-right. (i.e., where row_index == col_index).
  • The anti-diagonal (or secondary diagonal) consists of elements from the top-right to the bottom-left.

Requirement:

  • If the matrix has an odd dimension (e.g., 3x3, 5x5), the center element is part of both diagonals. Be careful not to count it twice in your total sum.

Test Cases:

Case 1: 4x4 Matrix (even dimension)

matrix_4x4 = [
	[ 1,  2,  3,  4],
	[ 5,  6,  7,  8],
	[ 9, 10, 11, 12],
	[13, 14, 15, 16]
]
# Primary diagonal: 1 + 6 + 11 + 16 = 34
# Anti-diagonal: 4 + 7 + 10 + 13 = 34
# Total sum = 34 + 34 = 68
# Expected Output: 68

Case 2: 3x3 Matrix (odd dimension)

matrix_3x3 = [
	[1, 2, 3],
	[4, 5, 6],
	[7, 8, 9]
]
# Primary diagonal: 1 + 5 + 9 = 15
# Anti-diagonal: 3 + 5 + 7 = 15
# The center element '5' is in both.
# Total sum = (1 + 5 + 9) + (3 + 7) = 15 + 10 = 25
# Expected Output: 25
Problem 4: Matrix Transposition

Problem Statement: In linear algebra, the transpose of a matrix is an operator which flips a matrix over its diagonal; that is, it switches the row and column indices of the matrix.

Write a function transpose_matrix(matrix) that takes a rectangular matrix (a non-empty list of lists where all inner lists have the same length) and returns its transpose.

For example, if the input matrix has dimensions M rows by N columns, the output matrix will have dimensions N rows by M columns. The element that was at matrix[row][col] will be at transposed_matrix[col][row].

Test Cases: Case 1: Rectangular Matrix (3x2)

matrix_3x2 = [
	[1, 2],
	[3, 4],
	[5, 6]
]
# Expected Output (a 2x3 matrix):
# [
#   [1, 3, 5],
#   [2, 4, 6]
# ]

Case 2: Square Matrix (2x2)

matrix_2x2 = [
	['a', 'b'],
	['c', 'd']
]
# Expected Output:
# [
#   ['a', 'c'],
#   ['b', 'd']
# ]
Problem 5: Leaderboard Sorting

Problem Statement: You are given a leaderboard for a game, represented as a list of tuples ('player_name', score). Your task is to write a function sort_leaderboard(leaderboard) that sorts this data and returns the sorted list.

The sorting must follow two rules in order:

  1. Primary Sort Key: Players should be sorted by their score in descending order (highest score first).
  2. Secondary Sort Key: If two or more players have the same score (a tie), they should be sorted by their player_name in ascending (alphabetical) order.

Constraint: You have not yet learned how to provide a custom key to the .sort() method. You must solve this problem by transforming the data into a temporary structure that can be sorted correctly using the default behavior of .sort().

Hint: Think about how Python sorts a list of tuples by default. It sorts by the first element, then the second for ties, and so on. How can you manipulate the score so that a standard ascending sort will achieve a descending result?

Test Cases: Case 1:

leaderboard = [
	('Alice', 88),
	('Bob', 92),
	('Charlie', 92),
	('David', 85)
]
# Sorting order: Bob (92), then Charlie (92, tie-broken by name), then Alice (88), then David (85)
# Expected Output: [('Bob', 92), ('Charlie', 92), ('Alice', 88), ('David', 85)]

Case 2:

scores = [('Zelda', 100), ('Mario', 120), ('Link', 100), ('Sonic', 100)]
# Expected Output: [('Mario', 120), ('Link', 100), ('Sonic', 100), ('Zelda', 100)]