(C++) Display the runtime after for loop

i'm new here and c++. I want to do bubble sort and calculate the runtime of the function. This is what i have done. It gives me output of the same statements. I only need the last answer to display. Thank you.

void bubblesort(int n)
{
    auto start_time = Clock::now();
    int* arr = new int[n];
    int* p;
    for(int i=0; i<n; i++){
        arr[i]=i+1;
    }
    int i, j;
    bool swapped; 
    int comparisons=0; 

    for (i = 0; i < n; i++)  {
      swapped = false;

    for (j = 0; j < n-i-1; j++)
    {
        comparisons++;
        if (arr[j] > arr[j+1])  
            {
                int temp = arr[j];
                arr[j]=arr[j+1];
                arr[j+1]=temp;
                swapped = true; 
            }

    //This is where i want to calculate the runtime but this will give output of many of this statement. 
    //I only want the last amount to be output

    auto end_time = Clock::now();
    std::cout << "Time difference: " << std::chrono::duration_cast<std::chrono::milliseconds>  
    (end_time - start_time).count() << " milliseconds" << std::endl;

    }
    if (swapped == false) 
        break; 
    }   
    cout << "Number of comparisons = " << comparisons << endl;
    delete[] arr;   
}