Welcome to The Coding College! In this tutorial, we will explore vectors in C++, one of the most versatile and widely used data structures provided by the Standard Template Library (STL).
What Are Vectors in C++?
A vector is a dynamic array that can resize itself automatically when elements are added or removed. Unlike regular arrays, vectors offer several useful member functions to manage data efficiently.
Key Features of Vectors:
- Dynamic size: Automatically adjusts its size to accommodate elements.
- Efficient access: Provides fast element access using indices.
- Versatile operations: Includes built-in functions like
push_back,pop_back, and more.
Declaring a Vector
You need to include the <vector> header to use vectors.
#include <vector>
#include <iostream>
using namespace std;
int main() {
vector<int> numbers; // Declare an empty vector of integers
vector<string> words = {"Hello", "World"}; // Vector with initial values
return 0;
}Adding Elements to a Vector
You can add elements to the end of a vector using the push_back method.
#include <vector>
#include <iostream>
using namespace std;
int main() {
vector<int> numbers;
numbers.push_back(10); // Add 10 to the vector
numbers.push_back(20); // Add 20 to the vector
numbers.push_back(30); // Add 30 to the vector
for (int num : numbers) {
cout << num << " ";
}
return 0;
}Output:
10 20 30 Accessing Vector Elements
You can access elements in a vector using an index (just like arrays).
#include <vector>
#include <iostream>
using namespace std;
int main() {
vector<int> numbers = {10, 20, 30};
cout << "First element: " << numbers[0] << endl;
cout << "Second element: " << numbers[1] << endl;
return 0;
}Output:
First element: 10
Second element: 20 Common Vector Operations
1. Size and Capacity
#include <vector>
#include <iostream>
using namespace std;
int main() {
vector<int> numbers = {10, 20, 30};
cout << "Size: " << numbers.size() << endl;
cout << "Capacity: " << numbers.capacity() << endl;
return 0;
}Output:
Size: 3
Capacity: 3 2. Remove Elements with pop_back
#include <vector>
#include <iostream>
using namespace std;
int main() {
vector<int> numbers = {10, 20, 30};
numbers.pop_back(); // Removes the last element
for (int num : numbers) {
cout << num << " ";
}
return 0;
}Output:
10 20 3. Insert Elements
You can insert an element at any position using insert.
#include <vector>
#include <iostream>
using namespace std;
int main() {
vector<int> numbers = {10, 20, 30};
numbers.insert(numbers.begin() + 1, 15); // Insert 15 at position 1
for (int num : numbers) {
cout << num << " ";
}
return 0;
}Output:
10 15 20 30 4. Remove Elements with erase
#include <vector>
#include <iostream>
using namespace std;
int main() {
vector<int> numbers = {10, 20, 30};
numbers.erase(numbers.begin() + 1); // Removes the element at position 1
for (int num : numbers) {
cout << num << " ";
}
return 0;
}Output:
10 30 5. Clear the Vector
The clear function removes all elements from the vector.
#include <vector>
#include <iostream>
using namespace std;
int main() {
vector<int> numbers = {10, 20, 30};
numbers.clear(); // Clear the vector
cout << "Size after clearing: " << numbers.size() << endl;
return 0;
}Output:
Size after clearing: 0 Iterating Over a Vector
You can use a range-based for loop or an iterator to iterate over a vector.
Using Range-Based For Loop
#include <vector>
#include <iostream>
using namespace std;
int main() {
vector<int> numbers = {10, 20, 30};
for (int num : numbers) {
cout << num << " ";
}
return 0;
}Using Iterators
#include <vector>
#include <iostream>
using namespace std;
int main() {
vector<int> numbers = {10, 20, 30};
for (vector<int>::iterator it = numbers.begin(); it != numbers.end(); ++it) {
cout << *it << " ";
}
return 0;
}Multi-Dimensional Vectors
Vectors can also store other vectors, creating multi-dimensional structures.
#include <vector>
#include <iostream>
using namespace std;
int main() {
vector<vector<int>> matrix = {
{1, 2, 3},
{4, 5, 6},
{7, 8, 9}
};
for (const auto& row : matrix) {
for (int num : row) {
cout << num << " ";
}
cout << endl;
}
return 0;
}Output:
1 2 3
4 5 6
7 8 9 Real-World Applications of Vectors
- Dynamic Arrays: Replace traditional arrays for flexible storage.
- 2D Grids: Create multi-dimensional vectors for simulations or games.
- Custom Data Handling: Store and manipulate user-defined types.
Summary
- Advantages: Vectors are dynamic, versatile, and efficient for most use cases.
- Common Functions: Use
push_back,pop_back,insert,erase,clear, etc. - Iterators: Provide flexibility for traversing and manipulating vectors.
Learn More at The Coding College
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