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

17 Jun, 2022
Vectors are the 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.
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.

Return Type: 
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
It has a no exception throw guarantee. 
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)
end() function is used to return an iterator pointing next to last element of the vector container. end() function returns a bidirectional iterator.
Syntax : 
vectorname.end()

Parameters :
No parameters are passed.

Return Type:
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
It has a no exception throw guarantee. Shows error when a parameter is passed.
It has a no exception throw guarantee. 
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) 
Let us see the differences in a tabular form is as follows:
Its syntax is -:
iterator begin();
Its syntax is -:
iterator end();
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