Better way to loop through user input - c++

Question

So I've been working on a little program that asks the user for the name/hours studying for a given topic, then does some calculations and displays the results back. Right now, to get the input for, say, 4 topics, I'm doing it this way:
#include <iostream>
using namespace std;
int main()
{
string topic1 = "";
string topic2 = "";
string topic3 = "";
string topic4 = "";
/* could have more topics here */
double hoursStudying1 = 0;
double hoursStudying2 = 0;
double hoursStudying3 = 0;
double hoursStudying4 = 0;
cout << "Topic name: ";
getline(cin, topic1);
cout << "Time studying for " << topic1 << ": ";
cin >> hoursStudying1;
cin.ignore();
cout << "Topic name: ";
getline(cin, topic2);
cout << "Time studying for " << topic2 << ": ";
cin >> hoursStudying2;
cin.ignore();
cout << "Topic name: ";
getline(cin, topic3);
cout << "Time studying for " << topic3 << ": ";
cin >> hoursStudying3;
cin.ignore();
/* calculate stuff here */
/* display the results */
cout << "For " << topic1 << " you spent " << hoursStudying1 << " hours studying" << endl;
/* etc */
return 0;
}
I'm a beginner, but I know there has to be a more efficient way to do this :(. How could I use, for example, a do...while loop or even a for loop to display a set number of prompts for each topic/hours studied (in order) as I'm doing now? I'm not looking for anyone to rewrite my program or anything like that, but rather give me some pointers with their code. Thanks a lot guys!
Edit: thank you so much for all the examples and pointers you've given me. I will play around with them and post some code of my own to let you know how it's working.

Answer 1

You will need to use an array or list, then loop through them. You can have two separate arrays, one to hold the topic names, and the other to hold the hours studies, or you can define a class that includes a topic name and hours studied and then have an array of elements of that class.
Bottom line, you need to learn how to use arrays or collections.

Answer 2

You can use a struct
typedef struct _element {
string topic;
double hoursStudying;
} element;
Then you can define an array of elements like this
element journal[ 4 ];
Now you can think of using loops to handle the array journal.
Try it yourself: write a complete program out of the above hints and let us know...
After doing that, try to transform the struct into a class figuring out what member functions are needed and then implementing them. Again, let us know...

Answer 3

I'd do something like:
cout << "Enter topic name or 'quit'";
while(true)
{
cin<< foo;
if(foo == 'quit')
break;
else
{
//Do stuff with foo
}
}
Obviously you'll want to handle weird input ("qUiT"), but that's the loop structure.

Answer 4

How could I use, for example, a do...while loop or even a for loop to display a set number of prompts for each topic/hours studied (in order) as I'm doing now?
Instead of creating a separate variable for, you should create an array to store your data. After that, use a loop to prompt and receive input. It can be a while-loop or a for-loop. (Generally, use a for-loop when you are certain how many times you want it to iterate. Use a while-loop when the number of times to iterate cannot be determined)
Example:
double hoursStudying[5] = {0};
for(int x=0; x<5; x++){ //5 can be replaced with a variable indicating array size
cout << "Time studying for " << topic << " " << x << ": ";
cin >> hoursStudying[x];
cin.ignore();
}
For displaying output, it will be the same. Just use a loop to iterate through the array values.
Example:
for(int x=0; x<5; x++){
cout << "For " << topic << " " << (x+1) << " you spent "
<< hoursStudying[x]<< " hours studying" << endl;
}

Answer 5

This is proper way to write programs in C++:
File Topic.h:
#pragma once
#include <sstream>
#include <string>
using namespace std;
class Topic {
string name;
double hours;
public:
Topic(string name, double hour);
~Topic();
void setName(const string & _name) {
name = _name;
}
void setHours(double & _hours) {
hours = _hours;
}
void addHours(double & _hours) {
hours += _hours;
}
string getName() const {
return name;
}
double getHours() const {
return hours;
}
string print() const;
};
File Topic.cpp
#include "Topic.h"
Topic::Topic(string name = "", double hour = 0.0) :
name(name), hours(hour) {
}
Topic::~Topic() {
}
string Topic::print() const {
ostringstream output;
output << "For " << name << " you spent " << hours << " hours studying.";
return output.str();
}
File Topics.h:
#pragma once
#include <vector>
#include <sstream>
#include <string>
#include "Topic.h"
using namespace std;
class Topics {
vector<Topic> topics;
public:
Topics();
~Topics();
void add(const Topic & topic) {
topics.push_back(topic);
}
Topic get(const unsigned int & index) const {
return topics[index];
}
string printAll() const;
};
File Topics.cpp:
#include "Topics.h"
Topics::Topics()
{
}
Topics::~Topics()
{
}
string Topics::printAll() const {
ostringstream output;
for (Topic topic : topics) {
output << topic.print() << endl;
}
return output.str();
}
File Source.cpp
#include <iostream>
#include <vector>
#include <sstream>
#include <string>
#include "Topic.h"
#include "Topics.h"
using namespace std;
Topic input() {
string name;
double hours;
cout << "Topic name: ";
cin >> name;
cout << "Time studying for " << name << ": ";
cin >> hours;
cout << endl;
return Topic(name, hours);
}
Topics inputCycle()
{
Topics topics;
int n;
cout << "How many topics you have ?" << endl;
cin >> n;
for (int i = 0; i < n; i++)
topics.add(input());
return topics;
}
void printAll(const Topics & topics) {
cout << topics.printAll() << endl;
}
int main()
{
printAll(inputCycle());
system("PAUSE");
return false;
}