Algorithms and Data Structures in C++: A Complete Guide for Beginners

Algorithms and Data Structures in C++: From Basics to Advanced Techniques

Algorithms and data structures are the foundation of any efficient program. In C++, you get full control over memory and performance, making this language ideal for learning algorithmic thinking. In this article, we will break down key concepts, provide code examples, and show how to apply them in practice. The material is suitable for both beginners and developers looking to systematize their knowledge.

We will cover three main groups: linear data structures (arrays, lists, stacks, queues), hierarchical structures (trees), and processing algorithms (sorting and searching). Each section contains ready-to-use C++ code and explanations.

1. Linear Data Structures: Arrays, Linked Lists, Stack, and Queue

Linear structures are the foundation for working with data. In C++, they are implemented both through built-in tools and through custom classes.

Arrays and Dynamic Arrays (std::vector)

An array is the simplest structure with a fixed size. For flexibility, use std::vector:

#include <iostream>#include <vector>

int main() {    std::vector<int> numbers = {5, 2, 8, 1, 9};        // Adding an element    numbers.push_back(3);        // Access by index    std::cout << "Third element: " << numbers[2] << std::endl;        // Iteration    for (int num : numbers) {        std::cout << num << " ";    }    return 0;}

Advantages: fast access O(1), cache locality. Disadvantages: insertion/deletion in the middle — O(n).

Linked List (Singly Linked)

A list consists of nodes, each storing data and a pointer to the next element. Implementation in C++:

struct Node {    int data;    Node* next;        Node(int val) : data(val), next(nullptr) {}};

class LinkedList {private:    Node* head;public:    LinkedList() : head(nullptr) {}        void pushFront(int val) {        Node* newNode = new Node(val);        newNode->next = head;        head = newNode;    }        void print() {        Node* current = head;        while (current) {            std::cout << current->data << " -> ";            current = current->next;        }        std::cout << "nullptr" << std::endl;    }        ~LinkedList() {        Node* current = head;        while (current) {            Node* next = current->next;            delete current;            current = next;        }    }};

When to use: frequent insertions/deletions at the beginning of the list. Search — O(n).

Stack and Queue

Stack (LIFO) and Queue (FIFO) are specialized structures. C++ has ready-made adapters:

#include <stack>#include <queue>

int main() {    // Stack    std::stack<int> st;    st.push(10);    st.push(20);    std::cout << "Top of stack: " << st.top() << std::endl; // 20    st.pop();        // Queue    std::queue<int> q;    q.push(1);    q.push(2);    std::cout << "First in queue: " << q.front() << std::endl; // 1    q.pop();        return 0;}

2. Hierarchical Structures: Binary Search Trees

Trees allow efficient storage of hierarchical data. Binary Search Tree (BST) is a classic in C++ algorithms.

BST Implementation

struct TreeNode {    int key;    TreeNode* left;    TreeNode* right;        TreeNode(int k) : key(k), left(nullptr), right(nullptr) {}};

TreeNode* insert(TreeNode* root, int key) {    if (!root) return new TreeNode(key);        if (key < root->key)        root->left =