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Algorithms & data structures

Classic patterns — search, sort, stacks, queues, and practical complexity-aware code.

3 matches

Implement Insert Delete GetRandom O(1) in Python

Build a RandomizedSet class that supports insert, delete, and get_random in average O(1) time using a list and a dictionary mapping values to indices.

randomized-set o1-lookup hash-map

Python

import random

class RandomizedSet:
    def __init__(self):
        self.values = []
        self.index_map = {}

    def insert(self, val):
        if val in self.index_map:
            return False
        self.index_map[val] = len(self.values)
        self.values.append(val)
        return True

    def delete(self…

12 0 Open

Algorithms & data structures easy

Implement Queue Using Two Stacks in Python

Python class that implements a FIFO queue using two stacks, with enqueue, dequeue, peek, and emptiness checks.

queue stack data-structures

Python

class QueueUsingStacks:
    def __init__(self):
        self.stack_in = []
        self.stack_out = []

    def enqueue(self, value):
        self.stack_in.append(value)

    def dequeue(self):
        if not self.stack_out:
            while self.stack_in:
                self.stack_out.append(self.stack_in.pop())
  …

13 0 Open

Algorithms & data structures easy

Implement a Stack Using List Push Pop in Python

A minimal Stack class built on a Python list, with push, pop, peek, is_empty, and size methods, including empty-stack guards.

stack data-structures list

Python

class Stack:
    def __init__(self):
        self.items = []

    def push(self, item):
        self.items.append(item)

    def pop(self):
        if self.is_empty():
            raise IndexError("pop from empty stack")
        return self.items.pop()

    def peek(self):
        if self.is_empty():
            raise…

12 0 Open

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