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What is the vector.front() function in C++?

Harsh Jain

Grokking Modern System Design Interview for Engineers & Managers

Ace your System Design Interview and take your career to the next level. Learn to handle the design of applications like Netflix, Quora, Facebook, Uber, and many more in a 45-min interview. Learn the RESHADED framework for architecting web-scale applications by determining requirements, constraints, and assumptions before diving into a step-by-step design process.

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In this shot, we will learn about vector::front() function in C++.

Introduction

The vector::front() function is available in the <vector> header file. This function returns a reference to the first element in the vector.

If we call the front() function on a vector that contains no elements, then we will get a segmentation fault error.

Syntax

The syntax of the vector::front() function is given below:

T& front();

Parameter

The vector::front() function does not accept any parameters.

Return

It returns a reference of the template-type object that points to the first element of the vector.

Code

Let’s have a look at the code now.

#include <iostream>
#include <vector>
using namespace std;
int main()
{
vector<int> vec;
// cout << " The Frontmost element of an empty vector is: " << vec.front();
vec.push_back(3);
vec.push_back(4);
vec.push_back(5);
vec.push_back(6);
vec.push_back(2);
cout << " The Frontmost element of the vector is: " << vec.front();
return 0;
}
Use vector.front() function in C++

Explanation

  • In line 1, we include the C++ standard header file for input/output stream (iostream) which is used to read and write from streams.

  • In line 2, we include the header file for C++ standard vector, which includes all the functions and operations related to the vector container.

  • In line 3, we use the standard (std) namespace that means we use all the things within the std namespace.

  • In line 7, we declare the integer type vector container named vec.

  • In line 9, we call the front() function on an empty vector. If you uncomment the line, then you will get a segmentation fault error as there is no element in the vector.

  • From line 11 to 15, we push back the different elements to the vector container vec.

  • In line 17, we print the result of the function front(), which returns the foremost element of the vector container and in this example, 33 is the front-most element. Hence the output is 3.

So, in this way, we can easily get the first element present in the vector.

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c++
communitycreator

Grokking Modern System Design Interview for Engineers & Managers

Ace your System Design Interview and take your career to the next level. Learn to handle the design of applications like Netflix, Quora, Facebook, Uber, and many more in a 45-min interview. Learn the RESHADED framework for architecting web-scale applications by determining requirements, constraints, and assumptions before diving into a step-by-step design process.

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