Gist file: https://gist.github.com/rjvitorino/7cee96329d41ef166172aeee743f6f33
Description: Cassidoo's interview question of the week: a function that takes an array of daily temperatures and returns an array where each element is the number of days you would have to wait until a warmer temperature. If there is no future day for which this is possible, put 0 instead.
from typing import List, Tuple
def daily_temperatures(temperatures: List[int]) -> List[int]:
"""
Calculates, for each day, the number of days expected until a warmer temperature.
If there is no future day for which a temperature is warmer, a 0 is returned.
:param temperatures: List of daily temperatures.
:return: List where each element is the number of days to wait for a warmer temperature.
"""
# Ensure all elements in the list are integers to prevent type errors during computation
if not all(isinstance(temperature, int) for temperature in temperatures):
raise ValueError("All elements in the temperatures list must be integers")
num_days: int = len(temperatures)
days_until_warmer: List[int] = [
0
] * num_days # Initialize the result list with zeros
stack: List[
int
] = [] # Stores indices of temperatures that are waiting for a warmer day
for current_day in range(num_days):
# Compare the current day's temperature with the temperatures of the days stored (stack)
# The stack keeps track of indices of days with unresolved warmer temperatures
while stack and temperatures[current_day] > temperatures[stack[-1]]:
previous_day: int = stack.pop() # Pop the index from the stack
# Calculate the number of days until a warmer temperature
days_until_warmer[previous_day] = current_day - previous_day
# Push the current day's index onto the stack to wait for a future warmer temperature
stack.append(current_day)
return days_until_warmer
def test_daily_temperatures() -> None:
"""
Tests the daily_temperatures function with various test cases.
:param None: No parameters
:return: None
"""
test_cases: List[Tuple[List[int], List[int]]] = [
# All temperatures are the same
([50, 50, 50, 50], [0, 0, 0, 0]),
# Strictly decreasing temperatures
([80, 70, 60, 50], [0, 0, 0, 0]),
# Strictly increasing temperatures
([50, 60, 70, 80], [1, 1, 1, 0]),
# Mixed temperatures with some fluctuations
([70, 72, 68, 76, 73, 71, 75, 74], [1, 2, 1, 0, 2, 1, 0, 0]),
# Single temperature
([60], [0]),
# Two temperatures, with increasing and decreasing scenarios
([60, 70], [1, 0]),
([70, 60], [0, 0]),
# Large input to test performance
([i for i in range(100, 0, -1)], [0] * 100),
# Randomised temperatures
([55, 50, 60, 58, 62, 53, 64, 49], [2, 1, 2, 1, 2, 1, 0, 0]),
# Alternating temperatures
([60, 70, 60, 70, 60, 70], [1, 0, 1, 0, 1, 0]),
# Temperatures with a plateau
([65, 65, 65, 70], [3, 2, 1, 0]),
# Empty list
([], []),
]
for index, (input, expected) in enumerate(test_cases):
result: List[int] = daily_temperatures(input)
assert (
result == expected
), f"Test case {index + 1} failed: expected {expected}, got {result}"
print(f"Test case {index + 1} passed!")
if __name__ == "__main__":
# Input from Cassidy
print(daily_temperatures([70, 70, 70, 75])) # [3, 2, 1, 0]
print(daily_temperatures([90, 80, 70, 60])) # [0, 0, 0, 0]
print(
daily_temperatures([73, 74, 75, 71, 69, 72, 76, 73])
) # [1, 1, 4, 2, 1, 1, 0, 0]
# Test other scenarios
test_daily_temperatures()