Thread: vector sourcing information problem

Okay in this vector array program I got it to print out the values in the input file number and price. How would i go about havng a question in the bottom somewhere asking a user for an item number , meaning first - 10 entrys in the input file.

for example here is my txt file.

100 13.43
101 10.99
102 3.45 (lets say i want the user to be able to type a number
of 3 and it will go and display this info.)
103 5.72
104 6.90
105 3.99
106 2.78
107 15.98
108 4.34
109 2.87
110 3.67

Here is my code so far:

Code:

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

using namespace std;

void main()
{
	vector<int> number;
	vector<double> price;

	int num;
	double pri;

	ifstream inFile("product.txt", ios::in);

	if(!inFile)
	{
		cerr<<"File could not be opened!"<<endl;
		exit(1);
	}

	while(!inFile.eof())
	{
		inFile >> num >> pri;
		number.push_back(num);
		price.push_back(pri);
	}

	cout << setw(10)<< "Product no." << setw(10) << "Price" << "\n";
	for(int i=0; i < number.size(); i++)
		cout << setw(10) << number[i] << setw(10) << price[i] << "\n";
}

salem

one the nag on the main() i have to do it that way for my class.

I know you are well respected in this forum , at least i see you post alot of stuff. But could you at least point a person in the right direction once in awhile instead of just nagging.

point taken. just following the book. i still need help with my problem.

This must be a bad time of the day for you. I asked the question at the top, not if my main and eof was correct. I can do those corrections , after i get on the right track on my problem.

i am asking if the data is set with a vector. How would i ask the question and have the program source the right values from the file.

I know how to do cout , cin. I am asking past that???

Well, obviously number and price are related, so it's not good style to make them paralell vectors. So.

Code:

struct Entry
{
    double price
    int number

    Entry(int p, int n) : price(p), number(n) { }
};

Code:

vector<Entry> v;

while(infile >> tempnumber >> tempprice)
{
    v.push_back(Entry(tempnumber, tempprice));
}

Code:

cout << v[usernumber].number << v[usernumber].price;

If I understood well, you need the user to input the number of something and the program will print the price for it. Well, there are some different ways, I will give you the most simple way I can imagine right now:

Code:

#include <vector>
#include <algorithm>
#include <iostream>

using namespace std;

int main() {

    vector<int> v;
    v.reserve( 10 );
    
    for(int i=0;i<=9;i++)
        v.push_back(i);
    
    int value;
    
    cin >> value;
    
    vector<int>::iterator position =
        find( v.begin(), v.end(), value);

    cout << "The value is " << *position << endl;

    return 0;
}

As you can see, I use find to find the position of the value I want. Once you have the iterator, you must use it to discover the number of the position:

Code:

int int_position = position - v.begin();
//use the int_position to access price vector

If it is not what you want, then ignore this post.