Algorithms & data structures
Classic patterns — search, sort, stacks, queues, and practical complexity-aware code.
Bucket Numbers into Histogram Bin Counts in Python
Partition a list of numbers into equal-width histogram bins and count how many fall into each bin using only the Python standard library.
from collections import Counter
def histogram_bins(numbers, num_bins):
"""Bucket numbers into histogram bin counts."""
if not numbers:
return []
min_val = min(numbers)
max_val = max(numbers)
bin_width = (max_val - min_val) / num_bins
# Handle edge case where all values are id…Extract n largest elements from a large list using heapq
Uses heapq.nlargest to efficiently extract the top n largest numbers from a large list, even with millions of elements.
import heapq
import random
def n_largest(numbers, n):
"""Return the n largest numbers from a list using heapq."""
if n <= 0:
return []
return heapq.nlargest(n, numbers)
if __name__ == "__main__":
# Create a large list with 1,000,000 random numbers
large_list = [random.randint(1, 1_000_000…Find Missing Number in Python Sequence 1 to N
Find the missing number from a list containing numbers 1 to N using the arithmetic sum formula.
def find_missing_number(nums, n):
expected_sum = n * (n + 1) // 2
actual_sum = sum(nums)
return expected_sum - actual_sum
if __name__ == "__main__":
n = 10
numbers = [1, 2, 3, 4, 5, 6, 7, 9, 10]
missing = find_missing_number(numbers, n)
print(f"The missing number is: {missing}")How to Generate Fibonacci Sequence in Python
Generate the first n Fibonacci numbers as a list using a simple iterative loop.
def fibonacci(n):
"""Generate the first n terms of the Fibonacci sequence."""
if n <= 0:
return []
seq = [0, 1]
while len(seq) < n:
seq.append(seq[-1] + seq[-2])
return seq[:n]
if __name__ == "__main__":
n = 10
result = fibonacci(n)
print(result)How to Sort Array by Parity (Even Before Odd) in Python
Rearrange an array so all even numbers appear before all odd numbers using a simple two-list partition approach.
def sort_array_by_parity(nums):
"""
Rearrange the array so that all even integers come first,
followed by all odd integers. The order within even and odd
groups is not required to be sorted.
"""
even = []
odd = []
for num in nums:
if num % 2 == 0:
even.append(nu…How to compress consecutive numbers into range strings in Python
Convert a sorted list of consecutive integers into compact range strings like '1-3', '5-6', and '15'.
def compress_ranges(nums):
"""Convert a list of sorted consecutive numbers into range strings."""
if not nums:
return []
ranges = []
start = prev = nums[0]
for num in nums[1:]:
if num == prev + 1:
prev = num
else:
if start == prev:
…Segregate Negative Numbers Before Positives in Python
Reorders a list so all negative numbers appear before non-negative numbers while preserving the original relative order of elements.
def segregate_negatives(numbers):
"""Segregate negatives before positives without altering relative order."""
negatives = [n for n in numbers if n < 0]
positives = [n for n in numbers if n >= 0]
return negatives + positives
if __name__ == "__main__":
sample = [3, -1, 4, -5, 2, -9, 0]
result =…Browse by section
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Algorithms & data structures — Python code examples
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