C++ Vector

In C++, a vector is a sequence container that is part of the C++ Standard Library, provided by the vector class. It is essentially a dynamic array, meaning it can automatically resize as elements are added or removed.

Methods for vector

push_back(value): Adds an element to the end of the vector.

pop_back(): Removes the last element.

size(): Returns the number of elements in the vector.

clear(): Removes all elements from the vector.

at(index): Provides safe access to an element (throws an exception if the index is out of range).

Example: Adding and Accessing Elements

#include <iostream>
#include <vector>
using namespace std;

int main() {
    // Creating a vector of integers
    vector<int> numbers;

    // Adding elements to the vector
    numbers.push_back(10);
    numbers.push_back(20);
    numbers.push_back(30);
    numbers.push_back(40);
    numbers.push_back(50);

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

    // Iterating through the vector using a range-based for loop
    cout << "Elements in the vector: ";
    for (int num : numbers) {
        cout << num << " ";
    }
    cout << endl;

    return 0;
}

Output:

Example: Resizing and Clearing a Vector

#include <iostream>
#include <vector>
using namespace std;

int main() {
    // Creating a vector of integers
    vector<int> nums = {10, 20, 30, 40, 50};

    // Resize the vector to have 2 elements
    nums.resize(2);
    cout << "After resizing to 2 elements: ";
    for (int num : nums) {
        cout << num << " ";
    }
    cout << std::endl;

    // Add new elements to the vector
    nums.push_back(3);
    nums.push_back(4);
    nums.push_back(5);

    cout << "After adding new elements: ";
    for (int num : nums) {
        cout << num << " ";
    }
    cout << endl;

    // Clear all elements from the vector
    nums.clear();
    cout << "After clearing, size of vector: " << nums.size() << std::endl;

    return 0;
}

Output:

Using pop_back() method to remove last element from the elements

#include <iostream>
#include <vector>
using namespace std;

int main() {
    // Creating a vector of integers
    vector<int> nums = {10, 20, 30, 40, 50};
    // remove last element
    nums.pop_back();
    cout << "list of elements: ";
    for (int num : nums) {
        cout << num << " ";
    }
 
    return 0;
}

Output:

Using at() method to get the element

#include <iostream>
#include <vector>
using namespace std;

int main() {
    // Creating a vector of integers
    vector<int> nums = {10, 20, 30, 40, 50};
    cout << "Get the First element: " << nums.at(2) << endl;
    cout << "Get the 4th element: " << nums.at(4);
  
    return 0;
}

Output:

C++ Vector – Questions and Answers

C++ Vector – Objective Questions (MCQs)

Related C++ Vector Topics