vector :: cbegin() and vector :: cend() in C++ STL

Vectors are known as dynamic arrays which can change its size automatically when an element is inserted or deleted. This storage is maintained by container.

vector::cbegin()

The function returns an iterator which is used to iterate container.

• The iterator points to the beginning of the vector.
• Iterator cannot modify the contents of the vector.

Syntax:

vectorname.cbegin()

Parameters: There is no parameter Return value: Constant random access iterator points to the beginning of the vector. Exception: No exception

Time Complexity – constant O(1)

Below program(s) illustrate the working of the function 

CPP

// CPP program to illustrate
// use of cbegin()
#include <iostream>
#include <string>
#include <vector>

using namespace std;

int main()
{
    vector<string> vec;

    // 5 string are inserted
    vec.push_back("first");
    vec.push_back("second");
    vec.push_back("third");
    vec.push_back("fourth");
    vec.push_back("fifth");

    // displaying the contents
    cout << "Contents of the vector:" << endl;
    for (auto itr = vec.cbegin();
         itr != vec.end();
         ++itr)
        cout << *itr << endl;

    return 0;
}

Output:

Contents of the vector:
first
second
third
fourth
fifth

vector::cend()

The function returns an iterator which is used to iterate container.

• The iterator points to past-the-end element of the vector.
• Iterator cannot modify the contents of the vector.

Syntax:

vectorname.cend()

Parameters: There is no parameter Return value: Constant random access iterator points to past-the-end element of the vector. Exception: No exception

Time Complexity – constant O(1)

Below program(s) illustrate the working of the function 

CPP

// CPP programto illustrate
// functioning of cend()
#include <iostream>
#include <string>
#include <vector>

using namespace std;

int main()
{
    vector<string> vec;

    // 5 string are inserted
    vec.push_back("first");
    vec.push_back("second");
    vec.push_back("third");
    vec.push_back("fourth");
    vec.push_back("fifth");

    // displaying the contents
    cout << "Contents of the vector:" << endl;
    for (auto itr = vec.cend() - 1;
         itr >= vec.begin();
         --itr)
        cout << *itr << endl;

    return 0;
}

Output:

Contents of the vector:
fifth
fourth
third
second
first