Question

Can someone explain how this C++ program runs?

A line by line explanation/commentation would be great, as well as the purpose of the program and functions/classes involved.

#include <iostream>

#include <vector>

using namespace std;

// template function

vector<int> removeEvenIndexedVals(vector<int> vec);

// main

int main() {

       static const int arr[] = { 2,5,7,9,1,3,6 };

       vector<int> vec(arr, arr + sizeof(arr) / sizeof(arr[0]));

       // call function

       vec = removeEvenIndexedVals(vec);

       // print

       cout << "Displaying the Vector Elements:" << endl;

       cout << "[ ";

       for (int i = 0; i<vec.size(); i++) {

              cout << vec[i] << " ";

       }

       cout << "]" << endl;

       system("pause");

       return 0;

}

// template function receives vector as a param

// return another vector that hold elements in odd index only

vector<int> removeEvenIndexedVals(vector<int> vec) {

       vector<int> v;

       for (int i = 0; i<vec.size(); i++) {

              if (i % 2 != 0) {

                     v.push_back(vec[i]);

              }

       }

       return v;

}

Answer 1

#include <iostream>

#include <vector>

using namespace std;

// template function

vector<int> removeEvenIndexedVals(vector<int> vec);

// main

int main() {
  
//Creating an array of type int
static const int arr[] = { 2,5,7,9,1,3,6 };

//Creating a Vector and initialize with array elements(arr)
vector<int> vec(arr, arr + sizeof(arr) / sizeof(arr[0]));

// call function

vec = removeEvenIndexedVals(vec);

// Displaying the elements in the vecor

cout << "Displaying the Vector Elements:" << endl;

cout << "[ ";

for (int i = 0; i<vec.size(); i++) {

cout << vec[i] << " ";

}

cout << "]" << endl;

system("pause");

return 0;

}

/* template function receives vector as a param
* This function will removes the even indexed values from
* vector(like 0,2,4,6 indexed values of vector)
* return another vector that hold elements in odd index only
*/

vector<int> removeEvenIndexedVals(vector<int> vec) {
  
//Creating a vector which holds integer values
vector<int> v;

/* Iterating over the Vector which passed as input
* and getting the values in the oodd indexes like (1,2,5...)
* and storing those values into another vector
*/
for (int i = 0; i<vec.size(); i++) {
  
/* Checking whether the index is odd or not
* if not odd discard it.
*/
if (i % 2 != 0) {

v.push_back(vec[i]);

}

}
//Returnig the new vector to the main()
return v;

}

______________

Output:

__________Thank You