Check out example codes for "vector in c". It will help you in understanding the concepts better.

Code Example 1

#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 cbegin and cend: "; 
    for (auto i = g1.cbegin(); i != g1.cend(); ++i) 
        cout << *i << " "; 
  
    cout << "\nOutput of rbegin and rend: "; 
    for (auto ir = g1.rbegin(); ir != g1.rend(); ++ir) 
        cout << *ir << " "; 
  
    cout << "\nOutput of crbegin and crend : "; 
    for (auto ir = g1.crbegin(); ir != g1.crend(); ++ir) 
        cout << *ir << " "; 
  
    return 0; 
}

Code Example 2

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 elements are placed in contiguous storage so that they can be accessed and traversed using iterators. In vectors, data is inserted at the end. Inserting at the end takes differential time, as sometimes there may be a need of extending the array. Removing the last element takes only constant time because no resizing happens. Inserting and erasing at the beginning or in the middle is linear in time.

 

Code Example 3

// 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] << " "; 
}

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