Arrays & Hashmaps

Master the fundamental building blocks of data structures

Progress

0 / 50 completed

Core Concepts

An array is a collection of items stored at contiguous memory locations. The idea is to store multiple items of the same type together.

A Hashmap (or Hash Table) is a data structure that implements an associative array abstract data type, a structure that can map keys to values.

// Initialization

vector<int> arr = {1, 2, 3};

vector<int> zeros(5, 0); // Size 5, all 0s

// Operations

arr.push_back(4); // O(1) amortized

arr.pop_back(); // O(1)

int x = arr[0]; // O(1) access

arr.size(); // O(1)

// Initialization

unordered_map<string, int> map;

// Operations

map["key"] = 10; // O(1) avg, O(n) worst

if (map.find("key") != map.end()) { ... }

map.erase("key"); // O(1) avg