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vector::begin() and vector::end() in C++ STL

  • Difficulty Level : Easy
  • Last Updated : 28 Oct, 2020
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Vectors are same as dynamic arrays with the ability to resize itself automatically when an element is inserted or deleted, with their storage being handled automatically by the container.

vector::begin()

begin() function is used to return an iterator pointing to the first element of the vector container. begin() function returns a bidirectional iterator to the first element of the container.
Syntax : 

vectorname.begin()
Parameters :
No parameters are passed.
Returns :
This function returns a bidirectional
iterator pointing to the first element.

Examples:  

Input  : myvector{1, 2, 3, 4, 5};
         myvector.begin();
Output : returns an iterator to the element 1

Input  : myvector{"This", "is", "Geeksforgeeks"};
         myvector.begin();
Output : returns an iterator to the element This

Errors and Exceptions
1. It has a no exception throw guarantee. 
2. Shows error when a parameter is passed. 

CPP




// INTEGER VECTOR EXAMPLE
// CPP program to illustrate
// Implementation of begin() function
#include <iostream>
#include <vector>
using namespace std;
 
int main()
{
    // declaration of vector container
    vector<int> myvector{ 1, 2, 3, 4, 5 };
 
    // using begin() to print vector
    for (auto it = myvector.begin();
         it != myvector.end(); ++it)
        cout << ' ' << *it;
    return 0;
}

Output: 



1 2 3 4 5

CPP




// STRING VECTOR EXAMPLE
// CPP program to illustrate
// Implementation of begin() function
#include <iostream>
#include <string>
#include <vector>
using namespace std;
 
int main()
{
    // declaration of vector container
    vector<string> myvector{ "This", "is",
                             "Geeksforgeeks" };
 
    // using begin() to print vector
    for (auto it = myvector.begin();
         it != myvector.end(); ++it)
        cout << ' ' << *it;
    return 0;
}

Output: 

This is Geeksforgeeks

Time Complexity: O(1)

vector::end()

end() function is used to return an iterator pointing to next to last element of the vector container. end() function returns a bidirectional iterator.
Syntax : 

vectorname.end()
Parameters :
No parameters are passed.
Returns :
This function returns a bidirectional
iterator pointing to next to last element.

Examples:  

Input  : myvector{1, 2, 3, 4, 5};
         myvector.end();
Output : returns an iterator after 5

Input  : myvector{"computer", "science", "portal"};
         myvector.end();
Output : returns an iterator after portal

Errors and Exceptions
1. It has a no exception throw guarantee. 
2. Shows error when a parameter is passed.

CPP




// INTEGER VECTOR EXAMPLE
// CPP program to illustrate
// Implementation of end() function
#include <iostream>
#include <vector>
using namespace std;
 
int main()
{
    // declaration of vector container
    vector<int> myvector{ 1, 2, 3, 4, 5 };
 
    // using end() to print vector
    for (auto it = myvector.begin();
         it != myvector.end(); ++it)
        cout << ' ' << *it;
    return 0;
}

Output: 

1 2 3 4 5

CPP




// STRING VECTOR EXAMPLE
// CPP program to illustrate
// Implementation of end() function
#include <iostream>
#include <string>
#include <vector>
using namespace std;
 
int main()
{
    // declaration of vector container
    vector<string> myvector{ "computer",
                             "science", "portal" };
 
    // using end() to print vector
    for (auto it = myvector.begin();
         it != myvector.end(); ++it)
        cout << ' ' << *it;
    return 0;
}

Output: 

computer science portal

Time Complexity: O(1) 

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