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vector::back() function with example in C++ STL

C++ STL vector::back() function: Here, we are going to learn about the back() function of vector header in C++ STL with example.
Submitted by IncludeHelp, on May 15, 2019

C++ vector::back() function

vector::back() is a library function of "vector" header, it is used to access the last element from the vector, it returns a reference to the last element of the vector.

Note: To use vector, include <vector> header.

Syntax of vector::back() function

    vector::back();

Parameter(s): none – It accepts nothing.

Return value: reference – It returns a reference to the last element of vector.

Example:

    Input:
    vector<int> vector1{ 1, 2, 3, 4, 5 };

    Function call:
    cout << vector1.back() << endl;

    Output:
    5

C++ program to demonstrate example of vector::back() function

//C++ STL program to demonstrate example of
//vector::back() function

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

int main()
{
    vector<int> v1{ 10, 20, 30, 40, 50 };

    //accessing last element
    //using vector::back() function

    cout << "last element is: " << v1.back() << endl;

    //changing last element
    v1.at(v1.size() - 1) = 100;
    cout << "now, last element is: " << v1.back() << endl;

    //changing last element
    //using push_back()
    v1.push_back(200);
    cout << "now, last element is: " << v1.back() << endl;

    return 0;
}

Output

last element is: 50
now, last element is: 100
now, last element is: 200

Reference: C++ vector::back()