Vector_STL.cpp

//Vector 

begin() – Returns an iterator pointing to the first element in the vector
end() – Returns an iterator pointing to the theoretical element that follows the last element in the vector
rbegin() – Returns a reverse iterator pointing to the last element in the vector (reverse beginning). It moves from last to first element
rend() – Returns a reverse iterator pointing to the theoretical element preceding the first element in the vector (considered as reverse end)

// C++ program to illustrate the iterators in vector
#include <iostream>
#include <vector>
  
using namespace std;
  
int main()
{
    vector<int> g1;
  
    for (int i = 1; i <= 5; i++)
        g1.push_back(i);
  
    cout << "Output of begin and end: ";
    for (auto i = g1.begin(); i != g1.end(); ++i)
        cout << *i << " ";
  
    cout << "\nOutput of rbegin and rend: ";
    for (auto ir = g1.rbegin(); ir != g1.rend(); ++ir)
        cout << *ir << " ";
  
    return 0;
}
Output:
Output of begin and end: 1 2 3 4 5 
Output of rbegin and rend: 5 4 3 2 1 

size() – Returns the number of elements in the vector.
max_size() – Returns the maximum number of elements that the vector can hold.
resize(n) – Resizes the container so that it contains ‘n’ elements.
empty() – Returns whether the container is empty.
shrink_to_fit() – Reduces the capacity of the container to fit its size and destroys all elements beyond the capacity.
reserve() – Requests that the vector capacity be at least enough to contain n elements.

// C++ program to illustrate the capacity function in vector
#include <iostream>
#include <vector>
  
using namespace std;
  
int main()
{
    vector<int> g1;
  
    for (int i = 1; i <= 5; i++)
        g1.push_back(i);
  
    cout << "Size : " << g1.size();
    cout << "\nMax_Size : " << g1.max_size();
  
    // resizes the vector size to 4
    g1.resize(4);
  
    // prints the vector size after resize()
    cout << "\nSize : " << g1.size();
  
    // checks if the vector is empty or not
    if (g1.empty() == false)
        cout << "\nVector is not empty";
    else
        cout << "\nVector is empty";
  
    // Shrinks the vector
    g1.shrink_to_fit();
    cout << "\nVector elements are: ";
    for (auto it = g1.begin(); it != g1.end(); it++)
        cout << *it << " ";
  
    return 0;
}
Output:
Size : 5
Max_Size : 4611686018427387903
Size : 4
Vector is not empty
Vector elements are: 1 2 3 4

reference operator [g] – Returns a reference to the element at position ‘g’ in the vector
at(g) – Returns a reference to the element at position ‘g’ in the vector
front() – Returns a reference to the first element in the vector
back() – Returns a reference to the last element in the vector

// C++ program to illustrate the element accesser in vector
#include <bits/stdc++.h>
using namespace std;
  
int main()
{
    vector<int> g1;
  
    for (int i = 1; i <= 10; i++)
        g1.push_back(i * 10);
  
    cout << "\nReference operator [g] : g1[2] = " << g1[2];
  
    cout << "\nat : g1.at(4) = " << g1.at(4);
  
    cout << "\nfront() : g1.front() = " << g1.front();
  
    cout << "\nback() : g1.back() = " << g1.back();
  
    return 0;
}
Output:
Reference operator [g] : g1[2] = 30
at : g1.at(4) = 50
front() : g1.front() = 10
back() : g1.back() = 100

assign() – It assigns new value to the vector elements by replacing old ones
push_back() – It push the elements into a vector from the back
pop_back() – It is used to pop or remove elements from a vector from the back.
insert() – It inserts new elements before the element at the specified position
erase() – It is used to remove elements from a container from the specified position or range.
swap() – It is used to swap the contents of one vector with another vector of same type. Sizes may differ.
clear() – It is used to remove all the elements of the vector container
emplace() – It extends the container by inserting new element at position
emplace_back() – It is used to insert a new element into the vector container, the new element is added to the end of the vector
.


// C++ program to illustrate the Modifiers in vector
#include <bits/stdc++.h>
#include <vector>
using namespace std;
  
int main()
{
    // Assign vector
    vector<int> v;
  
    // fill the array with 10 five times
    v.assign(5, 10);
  
    cout << "The vector elements are: ";
    for (int i = 0; i < v.size(); i++)
        cout << v[i] << " ";
  
    // inserts 15 to the last position
    v.push_back(15);
    int n = v.size();
    cout << "\nThe last element is: " << v[n - 1];
  
    // removes last element
    v.pop_back();
  
    // prints the vector
    cout << "\nThe vector elements are: ";
    for (int i = 0; i < v.size(); i++)
        cout << v[i] << " ";
  
    // inserts 5 at the beginning
    v.insert(v.begin(), 5);
  
    cout << "\nThe first element is: " << v[0];
  
    // removes the first element
    v.erase(v.begin());
  
    cout << "\nThe first element is: " << v[0];
  
    // inserts at the beginning
    v.emplace(v.begin(), 5);
    cout << "\nThe first element is: " << v[0];
  
    // Inserts 20 at the end
    v.emplace_back(20);
    n = v.size();
    cout << "\nThe last element is: " << v[n - 1];
  
    // erases the vector
    v.clear();
    cout << "\nVector size after erase(): " << v.size();
  
    // two vector to perform swap
    vector<int> v1, v2;
    v1.push_back(1);
    v1.push_back(2);
    v2.push_back(3);
    v2.push_back(4);
  
    cout << "\n\nVector 1: ";
    for (int i = 0; i < v1.size(); i++)
        cout << v1[i] << " ";
  
    cout << "\nVector 2: ";
    for (int i = 0; i < v2.size(); i++)
        cout << v2[i] << " ";
  
    // Swaps v1 and v2
    v1.swap(v2);
  
    cout << "\nAfter Swap \nVector 1: ";
    for (int i = 0; i < v1.size(); i++)
        cout << v1[i] << " ";
  
    cout << "\nVector 2: ";
    for (int i = 0; i < v2.size(); i++)
        cout << v2[i] << " ";
}
Output:
The vector elements are: 10 10 10 10 10 
The last element is: 15
The vector elements are: 10 10 10 10 10 
The first element is: 5
The first element is: 10
The first element is: 5
The last element is: 20
Vector size after erase(): 0

Vector 1: 1 2 
Vector 2: 3 4 
After Swap 
Vector 1: 3 4 
Vector 2: 1 2