Understanding Vectors in C++
Introduction
A vector in C++ is a dynamic array that can grow or shrink in size. It is part of the Standard Template Library (STL) and provides a safer and more flexible alternative to traditional arrays. Vectors are defined in the <vector> header and reside within the std namespace.
Creating a Vector
To create a vector, you need to include the <vector> header and use the std::vector template:
#include <vector>
#include <iostream>
int main() {
std::vector<int> numbers;
return 0;
}
Adding Elements to a Vector
You can add elements to a vector using the push_back method:
numbers.push_back(10);
numbers.push_back(20);
numbers.push_back(30);
This will add the elements 10, 20, and 30 to the vector.
Accessing Elements
Elements in a vector can be accessed using the [] operator or the at method:
int first = numbers[0];
int second = numbers.at(1);
The above code will access the first and second elements of the vector.
Iterating Over a Vector
You can iterate over a vector using a loop:
for (size_t i = 0; i < numbers.size(); ++i) {
std::cout << numbers[i] << " ";
}
This will print all the elements in the vector.
Removing Elements
To remove elements from a vector, you can use the pop_back method or the erase method:
numbers.pop_back();
// Removes the last element
numbers.erase(numbers.begin() + 1);
// Removes the second element
Vector Capacity
Vectors have several methods to manage their capacity:
numbers.size(); // Returns the number of elements
numbers.capacity(); // Returns the size of storage space currently allocated
numbers.reserve(10); // Requests that the vector capacity be at least enough to contain 10 elements
Clearing a Vector
To remove all elements from a vector, use the clear method:
numbers.clear();
This will remove all elements from the vector, reducing its size to 0.
Conclusion
Vectors are a powerful and flexible way to manage dynamic arrays in C++. They provide numerous methods for adding, accessing, and managing elements, making them an essential tool in any C++ programmer's toolkit. With this tutorial, you should now have a solid understanding of how vectors work and how to use them effectively.