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Algorithms & data structures

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3 matches

How to Find Four Sum Quadruplets in Python (Sorted Demo)

Find all unique quadruplets in a sorted array that sum to a target, with duplicate skipping.

def four_sum(nums, target):
    nums.sort()
    result = []
    n = len(nums)

    for i in range(n - 3):
        if i > 0 and nums[i] == nums[i - 1]:
            continue
        for j in range(i + 1, n - 2):
            if j > i + 1 and nums[j] == nums[j - 1]:
                continue
            left, right = j + 1…

13 0 Open

Algorithms & data structures medium

How to Find the n Smallest Items in a Large List with heapq in Python

This code demonstrates how to efficiently extract the n smallest items from a large list using Python's heapq module and a manual max-heap approach.

heapq heaps large data

Python

import heapq

def n_smallest_iterable(data, n):
    """Return the n smallest items without loading the whole list."""
    if n <= 0:
        return []
    return heapq.nsmallest(n, data)

def n_smallest_manual(data, n):
    """Return the n smallest using a heap, O(n log k) time."""
    if n <= 0:
        return []
   …

13 0 Open

Algorithms & data structures medium

Set Matrix Zeroes in Python: Markers List Grid Demo

Given a matrix, this code finds all rows and columns that contain a zero and sets every element in those rows and columns to zero, using boolean marker arrays.

matrix arrays algorithm

Python

def set_zeroes(matrix):
    rows, cols = len(matrix), len(matrix[0])
    row_markers = [False] * rows
    col_markers = [False] * cols

    # First pass: record which rows and columns contain zeros
    for i in range(rows):
        for j in range(cols):
            if matrix[i][j] == 0:
                row_markers[i] …

14 0 Open

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