C++ :: Stock Market Program - Sorting With Vectors

I'm writing a program of a stock market where i read from a file and sort with symbols and percent gain/loss. I have completed sorting with symbols but having trouble establishing the percent gain loss. First i designed and implemented the stock object. call the class stockType. main components of a stock are the stock symbol, stock price and number of shares. Second we have to create a list of stock objects. call the class to implement a list of stock objects stockListType. To store the list of stocks, i declared a vector and called the component type of this vector stockType. Because the company requires me to produce the list ordered by percent gain/loss, i need to sort the stock list by this component.

However, i'm not to physically sort the list by component percent gain/loss; instead i should provide a logic ordering with respect to this component. To do so i added a data member, a vector to hold the indices of the stock list ordered by the component percent gain/loss and i called this array indexByGain. I am going to use the array indexByGain to print the list. The elements of the array indexByGain will tell which component of the stock list to print next. I have trouble going about how to implement the function sortStockGain(). Below is my entire code and the txt file. I have sort symbols working but dont know how to implement the sort by gain.

Below is my entire code:

[#ifndef STOCKTYPE_H
#define STOCKTYPE_H

#include <iostream>
#include <fstream>
#include <iomanip>

using namespace std;
class stockType

[Code] ....