How to Print a Vector in C++?

If you’re a C++ programmer, you’ve likely encountered situations where you need to work with vectors, which are dynamic arrays commonly used to store elements of a given type. Printing the contents of a vector is a common task in programming, and there are several methods and techniques to achieve this. In this article, we will explore various methods for printing a vector in C++, including overloading the left shift operator (<<), using iterators, and employing functions like std::copy() and for_each(). Let’s dive into the world of vector printing in C++.

Understanding Vectors in C++

Before we delve into the different methods of printing vectors, let’s briefly understand what vectors are in C++. Vectors are similar to dynamic arrays, with the key difference being their automatic resizing capability. Vector elements are stored in contiguous memory locations, making it easier to access and traverse through the elements using iterators or pointers. When elements are added or removed from a vector, it’s referred to as insertion or deletion, and in such cases, printing the vector becomes essential.

Method 1: Overloading the Left Shift Operator (<<)

One of the elegant ways to print a vector in C++ is by overloading the left shift operator (<<). Operator overloading allows us to extend the functionality of operators while keeping their original meanings intact. In this case, we will overload the << operator to print vector elements.

Here’s an example of how to print a vector using operator overloading:

// C++ program to print a vector using << overloading
#include <iostream>
#include <vector>

using namespace std;

template <typename ele_type>
ostream& operator<<(ostream& os, const vector<ele_type>& vect_name) {
    for (auto itr : vect_name) {
        os << itr << " ";
    }
    return os;
}

int main() {
    vector<char> V = { 'A' , 'H', 'E', 'L', 'P' };
    cout << V << endl;
    return 0;
}

Output:

A H E L P

In this example, we define a template function that overloads the << operator. This function takes the output stream (ostream& os) and the vector (const vector<ele_type>& vect_name) as arguments and iterates over the vector’s elements to print them.

Method 2: Using Iterators

Another way to print a vector in C++ is by using iterators. Iterators are markers or pointers that indicate the position of an element in a vector. By employing constant iterators (cbegin() and cend()), we can easily print the elements of a vector.

Here’s an example of printing a vector using iterators:

// C++ program to print vectors using iterators
#include <iostream>
#include <vector>

using namespace std;

template <typename ele_type>
void print(const vector<ele_type>& V) {
    for (auto itr = V.cbegin(); itr != V.cend(); ++itr) {
        cout << *itr << " ";
    }
}

int main() {
    vector<char> V = { 'A' , 'H', 'E', 'L', 'P' };
    print(V);
    cout << endl;
    return 0;
}

Output:

A H E L P

In this example, we define a template function named print(), which takes a vector as an input argument. We use a for loop with iterators to traverse the vector and print its elements.

Method 3: Using std::copy() Function

The std::copy() function, part of the C++ Algorithm Library, can be utilized to copy a range of elements from a vector to an output stream like cout. This function simplifies the process of printing vector contents.

Here’s an example of printing a vector using the std::copy() function:

// C++ program to print vectors using the copy function
#include <iostream>
#include <algorithm>
#include <iterator>
#include <vector>

using namespace std;

template <typename ele_type>
void print(const vector<ele_type>& V) {
    copy(V.begin(), V.end(), ostream_iterator<ele_type>(cout, " "));
}

int main() {
    vector<char> V = { 'A' , 'H', 'E', 'L', 'P' };
    print(V);
    cout << endl;
    return 0;
}

Output:

A H E L P

In this example, we define a template function print() that uses the std::copy() function to copy the vector’s elements to the output stream (cout) using ostream_iterator. This method provides a concise way to print vector contents.

Method 4: Using the for_each() Function

The for_each() function in C++ offers an elegant way to print vector elements. It takes three input arguments: a start iterator, an end iterator, and a function. The function is applied to each element within the specified range, making it efficient for printing vector elements.

Here’s an example of printing a vector using the for_each() function:

// C++ program to print vector using for_each() function
#include <iostream>
#include <algorithm>
#include <vector>
#include <string>

using namespace std;

void print(const string &i) {
    cout << i << ' ';
}

int main() {
    vector<string> V = { "Get", "Mentors", "And", "Grow" };
    for_each(V.begin(), V.end(), print);
    cout << endl;
    return 0;
}

Output:

Get Mentors And Grow 

In this example, we define a function print() that takes a vector element as input and prints it followed by a space. We then use the for_each() function to apply this function to each element in the vector, effectively printing all the elements.

Conclusion

In this article, we explored various methods and techniques for printing vectors in C++. Whether you prefer overloading the left shift operator, using iterators, employing the std::copy() function, or leveraging the for_each() function, you have multiple options at your disposal. These methods provide flexibility and efficiency, allowing you to choose the one that best suits your programming needs. With this knowledge, you can confidently work with vectors in C++ and efficiently print their contents. Happy coding!

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