How to find the second Largest Contour in an image

edit

All the while, the example of coding is to calculate the biggest of the smallest area of contour in an image. Is there any idea on how to get the second largest contour area from opencv C++? I believe i can find the second largest area, but the index .. My code is quite messy sorry for that.

here is to find the biggest one.

// iterate through each contour.
for( int i = 0; i< contours.size(); i++ )
{
//  Find the area of contour
double a=contourArea( contours[i],false); 
    arrayarea[i]=a;

if(a>largest_area)

    {
    largest_area=a;cout<<i<<" area  "<<a<<endl;
        // Store the index of largest contour
    largest_contour_index=i;               
    cerr << largest_contour_index << "largest_contour_index" << endl;
        // Find the bounding rectangle for biggest contour
        //bounding_rect=boundingRect(contours[i]);
    }

        cerr << arrayarea[i] << "arrayarea[i]" << endl;
}

    waitKey(0);
    first = second = INT_MIN;
for (i = 0; i < arrayarea[i] ; i ++)
{
    /* If current element is smaller than first
       then update both first and second */
    if (arrayarea[i] > first)
    {
        second = first;
        first = arrayarea[i];
}

/* If arr[i] is in between first and 
   second then update second  */
    else if (arrayarea[i] > second && arrayarea[i] != first)
        second = arrayarea[i];
}

if (second == INT_MIN)
    printf("There is no second largest element\n");
else
    printf("The second largest element is %dn", second);