Use STL Components in C++

Introduction

In this lab, you will learn how to use various components of the C++ Standard Template Library (STL) to create and manipulate data structures such as vectors, lists, maps, sets, and more. You'll explore the basic operations of these STL containers, including adding, removing, and iterating through elements. Additionally, you'll discover how to leverage STL algorithms for sorting, searching, and processing data within these containers. By the end of this lab, you will have a solid understanding of how to leverage the power and flexibility of the C++ STL to build efficient and robust applications.

Skills Graph

Create and Manipulate Vector Container

In this step, you'll learn about the C++ Standard Template Library (STL) vector container, which is a dynamic array that can grow and shrink in size. Vectors are incredibly useful for storing and manipulating collections of elements.

First, open the WebIDE and create a new file called vector_demo.cpp in the ~/project directory. We'll explore the basic operations of vectors step by step.

touch ~/project/vector_demo.cpp

Add the following code to the vector_demo.cpp file:

#include <iostream>
#include <vector>

int main() {
    // Create an empty vector of integers
    std::vector<int> numbers;

    // Add elements to the vector using push_back()
    numbers.push_back(10);
    numbers.push_back(20);
    numbers.push_back(30);

    // Print the size of the vector
    std::cout << "Vector size: " << numbers.size() << std::endl;

    // Access elements using index
    std::cout << "First element: " << numbers[0] << std::endl;
    std::cout << "Second element: " << numbers[1] << std::endl;

    // Iterate through the vector using a range-based for loop
    std::cout << "All elements: ";
    for (int num : numbers) {
        std::cout << num << " ";
    }
    std::cout << std::endl;

    // Remove the last element
    numbers.pop_back();

    // Check the new size after removing an element
    std::cout << "Vector size after pop_back(): " << numbers.size() << std::endl;

    return 0;
}

Compile and run the program:

g++ vector_demo.cpp -o vector_demo
./vector_demo

Example output:

Vector size: 3
First element: 10
Second element: 20
All elements: 10 20 30
Vector size after pop_back(): 2

Key points about vectors:

• Use #include <vector> to include the vector library
• std::vector<type> creates a vector of a specific type
• push_back() adds elements to the end of the vector
• size() returns the number of elements
• Access elements using index []
• pop_back() removes the last element
• Range-based for loop is an easy way to iterate through vectors

Use List for Linked List Operations

In this step, you'll learn about the C++ STL list container, which implements a doubly-linked list. Lists provide efficient insertion and deletion operations at any position in the container.

Open the WebIDE and create a new file called list_demo.cpp in the ~/project directory:

touch ~/project/list_demo.cpp

Add the following code to the list_demo.cpp file:

#include <iostream>
#include <list>

int main() {
    // Create an empty list of integers
    std::list<int> numbers;

    // Add elements to the list
    numbers.push_back(10);    // Add to the end
    numbers.push_front(5);    // Add to the beginning
    numbers.push_back(20);

    // Print the list size
    std::cout << "List size: " << numbers.size() << std::endl;

    // Iterate through the list
    std::cout << "List elements: ";
    for (int num : numbers) {
        std::cout << num << " ";
    }
    std::cout << std::endl;

    // Remove elements
    numbers.pop_front();  // Remove first element
    numbers.pop_back();   // Remove last element

    // Insert an element at a specific position
    auto it = numbers.begin();
    numbers.insert(it, 15);

    // Print updated list
    std::cout << "Updated list: ";
    for (int num : numbers) {
        std::cout << num << " ";
    }
    std::cout << std::endl;

    // Check if list is empty
    std::cout << "Is list empty? "
              << (numbers.empty() ? "Yes" : "No") << std::endl;

    return 0;
}

Compile and run the program:

g++ list_demo.cpp -o list_demo
./list_demo

Example output:

List size: 3
List elements: 5 10 20
Updated list: 15 10
Is list empty? No

Key points about lists:

• Use #include <list> to include the list library
• push_back() adds elements to the end
• push_front() adds elements to the beginning
• pop_front() and pop_back() remove elements
• insert() allows adding elements at a specific position
• begin() returns an iterator to the first element
• empty() checks if the list is empty

Implement Key-Value Pairs with Map

In this step, you'll learn about the C++ STL map container, which stores key-value pairs in a sorted and unique key order. Maps are useful for creating dictionaries or associative arrays.

Open the WebIDE and create a new file called map_demo.cpp in the ~/project directory:

touch ~/project/map_demo.cpp

Add the following code to the map_demo.cpp file:

#include <iostream>
#include <map>
#include <string>

int main() {
    // Create a map to store student names and their ages
    std::map<std::string, int> students;

    // Insert key-value pairs
    students["Alice"] = 20;
    students["Bob"] = 22;
    students["Charlie"] = 21;

    // Access values using keys
    std::cout << "Alice's age: " << students["Alice"] << std::endl;

    // Check if a key exists
    if (students.count("David") == 0) {
        std::cout << "David is not in the map" << std::endl;
    }

    // Iterate through the map
    std::cout << "All students:" << std::endl;
    for (const auto& student : students) {
        std::cout << student.first << ": " << student.second << std::endl;
    }

    // Remove a key-value pair
    students.erase("Bob");

    // Check the size of the map
    std::cout << "Number of students: " << students.size() << std::endl;

    return 0;
}

Compile and run the program:

g++ map_demo.cpp -o map_demo
./map_demo

Example output:

Alice's age: 20
David is not in the map
All students:
Alice: 20
Bob: 22
Charlie: 21
Number of students: 2

Key points about maps:

• Use #include <map> to include the map library
• map<KeyType, ValueType> creates a map with specified key and value types
• Access values using square brackets []
• count() checks if a key exists
• Iterate through maps using range-based for loop
• erase() removes a key-value pair
• size() returns the number of elements

Store Unique Elements Using Set

In this step, you'll learn about the C++ STL set container, which stores unique elements in a sorted order. Sets automatically prevent duplicate values and maintain elements in a specific order.

Open the WebIDE and create a new file called set_demo.cpp in the ~/project directory:

touch ~/project/set_demo.cpp

Add the following code to the set_demo.cpp file:

#include <iostream>
#include <set>

int main() {
    // Create a set of integers
    std::set<int> numbers;

    // Insert elements
    numbers.insert(10);
    numbers.insert(20);
    numbers.insert(30);
    numbers.insert(10);  // Duplicate, will not be added

    // Print the size of the set
    std::cout << "Set size: " << numbers.size() << std::endl;

    // Iterate through the set
    std::cout << "Set elements: ";
    for (int num : numbers) {
        std::cout << num << " ";
    }
    std::cout << std::endl;

    // Check if an element exists
    if (numbers.count(20) > 0) {
        std::cout << "20 is in the set" << std::endl;
    }

    // Remove an element
    numbers.erase(20);

    // Check the size after removal
    std::cout << "Set size after removal: " << numbers.size() << std::endl;

    // Clear the set
    numbers.clear();

    // Check if the set is empty
    std::cout << "Is set empty? "
              << (numbers.empty() ? "Yes" : "No") << std::endl;

    return 0;
}

Compile and run the program:

g++ set_demo.cpp -o set_demo
./set_demo

Example output:

Set size: 3
Set elements: 10 20 30
20 is in the set
Set size after removal: 2
Is set empty? Yes

Key points about sets:

• Use #include <set> to include the set library
• set<type> creates a set of unique elements
• insert() adds elements (duplicates are ignored)
• count() checks element existence
• erase() removes an element
• clear() removes all elements
• empty() checks if the set is empty
• Elements are automatically sorted

Sort Elements with STL sort Algorithm

In this step, you'll learn how to use the STL sort algorithm to arrange elements in ascending or descending order. The <algorithm> library provides powerful sorting capabilities for various containers.

Open the WebIDE and create a new file called sort_demo.cpp in the ~/project directory:

touch ~/project/sort_demo.cpp

Add the following code to the sort_demo.cpp file:

#include <iostream>
#include <vector>
#include <algorithm>

int main() {
    // Create a vector of integers
    std::vector<int> numbers = {5, 2, 8, 1, 9, 3};

    // Print original vector
    std::cout << "Original vector: ";
    for (int num : numbers) {
        std::cout << num << " ";
    }
    std::cout << std::endl;

    // Sort the vector in ascending order
    std::sort(numbers.begin(), numbers.end());

    // Print sorted vector
    std::cout << "Sorted vector (ascending): ";
    for (int num : numbers) {
        std::cout << num << " ";
    }
    std::cout << std::endl;

    // Sort the vector in descending order
    std::sort(numbers.begin(), numbers.end(), std::greater<int>());

    // Print vector sorted in descending order
    std::cout << "Sorted vector (descending): ";
    for (int num : numbers) {
        std::cout << num << " ";
    }
    std::cout << std::endl;

    return 0;
}

Compile and run the program:

g++ sort_demo.cpp -o sort_demo
./sort_demo

Example output:

Original vector: 5 2 8 1 9 3
Sorted vector (ascending): 1 2 3 5 8 9
Sorted vector (descending): 9 8 5 3 2 1

Key points about STL sort:

• Include <algorithm> library for sorting
• std::sort() works with various containers
• Default sorting is in ascending order
• std::greater<type>() sorts in descending order
• Sorting is done in-place, modifying the original container
• Works efficiently with different container types

Find Elements Using STL Algorithms

In this step, you'll learn how to use STL algorithms to find and search for elements in containers. The <algorithm> library provides powerful functions for searching and locating elements.

Open the WebIDE and create a new file called find_demo.cpp in the ~/project directory:

touch ~/project/find_demo.cpp

Add the following code to the find_demo.cpp file:

#include <iostream>
#include <vector>
#include <algorithm>

int main() {
    // Create a vector of integers
    std::vector<int> numbers = {5, 2, 8, 1, 9, 3, 8};

    // Find first occurrence of a specific element
    auto it = std::find(numbers.begin(), numbers.end(), 8);
    if (it != numbers.end()) {
        std::cout << "First occurrence of 8 at index: "
                  << std::distance(numbers.begin(), it) << std::endl;
    }

    // Count occurrences of an element
    int count = std::count(numbers.begin(), numbers.end(), 8);
    std::cout << "Number of 8s in the vector: " << count << std::endl;

    // Find if any element is greater than 6
    bool has_large_element = std::any_of(numbers.begin(), numbers.end(),
        [](int n) { return n > 6; });
    std::cout << "Vector has element > 6: "
              << (has_large_element ? "Yes" : "No") << std::endl;

    // Find the minimum and maximum elements
    auto min_it = std::min_element(numbers.begin(), numbers.end());
    auto max_it = std::max_element(numbers.begin(), numbers.end());

    std::cout << "Minimum element: " << *min_it << std::endl;
    std::cout << "Maximum element: " << *max_it << std::endl;

    return 0;
}

Compile and run the program:

g++ find_demo.cpp -o find_demo
./find_demo

Example output:

First occurrence of 8 at index: 2
Number of 8s in the vector: 2
Vector has element > 6: Yes
Minimum element: 1
Maximum element: 9

Key points about STL search algorithms:

• std::find() locates first occurrence of an element
• std::count() counts element occurrences
• std::any_of() checks if any element meets a condition
• std::min_element() and std::max_element() find extreme values
• Lambda functions can be used for custom search conditions
• Return iterators point to found elements

Iterate Through Containers

In this step, you'll learn different ways to iterate through STL containers using various iteration techniques. We'll explore range-based for loops, iterators, and traditional index-based iteration.

Open the WebIDE and create a new file called iteration_demo.cpp in the ~/project directory:

touch ~/project/iteration_demo.cpp

Add the following code to the iteration_demo.cpp file:

#include <iostream>
#include <vector>
#include <list>
#include <map>

int main() {
    // Vector iteration
    std::vector<int> numbers = {10, 20, 30, 40, 50};

    // Method 1: Range-based for loop (most modern and readable)
    std::cout << "Vector iteration (range-based for):" << std::endl;
    for (int num : numbers) {
        std::cout << num << " ";
    }
    std::cout << std::endl;

    // Method 2: Iterator-based iteration
    std::cout << "Vector iteration (iterators):" << std::endl;
    for (auto it = numbers.begin(); it != numbers.end(); ++it) {
        std::cout << *it << " ";
    }
    std::cout << std::endl;

    // Method 3: Index-based iteration
    std::cout << "Vector iteration (index-based):" << std::endl;
    for (size_t i = 0; i < numbers.size(); ++i) {
        std::cout << numbers[i] << " ";
    }
    std::cout << std::endl;

    // Map iteration
    std::map<std::string, int> ages = {
        {"Alice", 25},
        {"Bob", 30},
        {"Charlie", 35}
    };

    std::cout << "Map iteration:" << std::endl;
    for (const auto& pair : ages) {
        std::cout << pair.first << ": " << pair.second << std::endl;
    }

    return 0;
}

Compile and run the program:

g++ iteration_demo.cpp -o iteration_demo
./iteration_demo

Example output:

Vector iteration (range-based for):
10 20 30 40 50
Vector iteration (iterators):
10 20 30 40 50
Vector iteration (index-based):
10 20 30 40 50
Map iteration:
Alice: 25
Bob: 30
Charlie: 35

Key points about container iteration:

• Range-based for loops are the most modern and readable
• Iterators provide fine-grained control over container traversal
• Index-based iteration works well with random-access containers
• auto keyword helps with type inference
• Different containers support different iteration methods

Use STL Stack and Queue

In this step, you'll learn about two important STL container adapters: stack and queue. These containers provide specialized operations for last-in-first-out (LIFO) and first-in-first-out (FIFO) data management.

Open the WebIDE and create a new file called stack_queue_demo.cpp in the ~/project directory:

touch ~/project/stack_queue_demo.cpp

Add the following code to the stack_queue_demo.cpp file:

#include <iostream>
#include <stack>
#include <queue>

int main() {
    // Stack demonstration
    std::stack<int> myStack;

    // Push elements onto the stack
    myStack.push(10);
    myStack.push(20);
    myStack.push(30);

    std::cout << "Stack operations:" << std::endl;
    std::cout << "Top element: " << myStack.top() << std::endl;

    // Remove top element
    myStack.pop();
    std::cout << "Top element after pop: " << myStack.top() << std::endl;
    std::cout << "Stack size: " << myStack.size() << std::endl;

    // Queue demonstration
    std::queue<std::string> myQueue;

    // Add elements to the queue
    myQueue.push("Alice");
    myQueue.push("Bob");
    myQueue.push("Charlie");

    std::cout << "\nQueue operations:" << std::endl;
    std::cout << "Front element: " << myQueue.front() << std::endl;
    std::cout << "Back element: " << myQueue.back() << std::endl;

    // Remove front element
    myQueue.pop();
    std::cout << "Front element after pop: " << myQueue.front() << std::endl;
    std::cout << "Queue size: " << myQueue.size() << std::endl;

    return 0;
}

Compile and run the program:

g++ stack_queue_demo.cpp -o stack_queue_demo
./stack_queue_demo

Example output:

Stack operations:
Top element: 30
Top element after pop: 20
Stack size: 2

Queue operations:
Front element: Alice
Back element: Charlie
Front element after pop: Bob
Queue size: 2

Key points about stack and queue:

• Stack (LIFO - Last In, First Out)
  • push() adds element to the top
  • pop() removes top element
  • top() returns the top element
• Queue (FIFO - First In, First Out)
  • push() adds element to the back
  • pop() removes front element
  • front() returns the first element
  • back() returns the last element
• Both have size() method to check number of elements
• Include <stack> and <queue> headers

Handle Container Exception Safety

In this step, you'll learn how to handle exceptions and ensure safe operations with STL containers. Exception handling helps prevent program crashes and provides robust error management.

Open the WebIDE and create a new file called exception_safety_demo.cpp in the ~/project directory:

touch ~/project/exception_safety_demo.cpp

Add the following code to the exception_safety_demo.cpp file:

#include <iostream>
#include <vector>
#include <stdexcept>

void demonstrateVectorSafety() {
    std::vector<int> numbers;

    try {
        // Attempt to access an element from an empty vector
        std::cout << "Attempting to access element from empty vector:" << std::endl;
        numbers.at(0);  // This will throw an out_of_range exception
    }
    catch (const std::out_of_range& e) {
        std::cout << "Out of Range Error: " << e.what() << std::endl;
    }

    // Safe element addition
    try {
        numbers.push_back(10);
        numbers.push_back(20);
        std::cout << "Vector size: " << numbers.size() << std::endl;

        // Safe element access
        std::cout << "First element: " << numbers.at(0) << std::endl;
        std::cout << "Second element: " << numbers.at(1) << std::endl;
    }
    catch (const std::exception& e) {
        std::cout << "An error occurred: " << e.what() << std::endl;
    }
}

int main() {
    // Demonstrate vector exception safety
    demonstrateVectorSafety();

    return 0;
}

Compile and run the program:

g++ exception_safety_demo.cpp -o exception_safety_demo
./exception_safety_demo

Example output:

Attempting to access element from empty vector:
Out of Range Error: vector
Vector size: 2
First element: 10
Second element: 20

Key points about container exception safety:

• Use try-catch blocks to handle potential exceptions
• std::out_of_range is thrown when accessing invalid vector elements
• at() method performs bounds checking, unlike [] operator
• Catch specific exceptions first, then more general ones
• Always handle potential exceptions to prevent program crashes
• Use standard exception classes from <stdexcept>

Summary

In this lab, you learned about various components of the C++ Standard Template Library (STL) and how to use them effectively. You started by exploring the vector container, which is a dynamic array that can grow and shrink in size. You learned how to add and remove elements, access them using indices, and iterate through the vector using a range-based for loop.

Next, you delved into the list container, which is a doubly-linked list implementation. You discovered how to perform common linked list operations such as inserting, deleting, and traversing elements. You also explored the map container, which allows you to store key-value pairs, and the set container, which stores unique elements. Additionally, you learned how to use STL algorithms like sort and find to manipulate and search elements within these containers. Finally, you explored the stack and queue containers, and discussed the importance of exception safety when working with STL components.