from collections import Counter
import random
"""
Goal:
- Select N random values that appear exactly once in the list.
- The list includes duplicates, but only values with frequency = 1
are eligible for selection.
Approach:
1. Count frequencies using collections.Counter.
2. Collect values that appear exactly once.
3. Randomly sample N values using random.sample.
4. Return them and print them.
Notes:
- Uses Python's built-in tools for clarity and efficiency.
- Uses structured, expressive functions.
"""
#---------------------------------------------------------------
# Build a frequency map: value -> count
#---------------------------------------------------------------
def build_frequency_map(data):
# Counter returns a dictionary-like object: value -> count
return Counter(data)
#---------------------------------------------------------------
# Collect values that appear exactly once
#---------------------------------------------------------------
def collect_globally_unique_values(data, freq):
unique = []
for value in data:
if freq[value] == 1:
unique.append(value)
return unique
#---------------------------------------------------------------
# Randomly select N values from the unique list
#---------------------------------------------------------------
def select_random_unique(unique, N):
# Clamp N to available unique values
if N > len(unique):
N = len(unique)
# random.sample selects N distinct elements without replacement
return random.sample(unique, N)
#---------------------------------------------------------------
# Print helper
#---------------------------------------------------------------
def print_list(lst):
print(" ".join(str(v) for v in lst))
#---------------------------------------------------------------
# Main program
#---------------------------------------------------------------
if __name__ == "__main__":
# Example list with duplicates
data = [
5, 12, 5, 19, 5, 33, 19, 5, 8, 8, 8, 59, 61, 17, 3, 5, 3, 74, 83, 90, 3, 1
]
# Step 1: Build frequency map
freq = build_frequency_map(data)
# Step 2: Collect values that appear exactly once
unique_values = collect_globally_unique_values(data, freq)
# Step 3: Choose how many unique random values to select
N = 5
# Step 4: Select N random unique values
random_selection = select_random_unique(unique_values, N)
# Step 5: Print results
print("Values that appear exactly once:")
print_list(unique_values)
print("\nRandom selection ({} values):".format(N))
print_list(random_selection)
"""
run:
Values that appear exactly once:
12 33 59 61 17 74 83 90 1
Random selection (5 values):
12 59 1 90 17
"""
