CODEWITHSUNDEEP
c++
sara8
sara8

Reputation: 209

c++ read and write numeric numbers from text file using vector

I learn a course from coursera. In one of the lesson ther is a code which supposed to perform read and write numeric numbers from text file using vector. This is the code:

#include <iostream>
#include <iterator>
#include <fstream>
#include <vector>
#include "Student.h"
//#include ""
using namespace std;


int main()
{
    /*cout << "Hello School!" << endl;
    Student sarit_student("Sarit Rotshild",12345);*/
    ifstream data_file("../../sarit/data.text");
    istream_iterator<int> start(data_file), end;
    vector<int> data(start, end);
    int sum=0;
    for(auto it=start; it!=end; ++it)
    {
        sum+= *it;
    }
    cout<<"sum = "<< sum<<endl;
    cout<<"avg is : "<< 1.0* sum/data.size()<<endl;
    return 0;235
}

The input (in the text file) is 12 15 18 23 235 However the out put that I got is not correct---> sum = 12 avg is : 2.4

Upvotes: 2

Views: 125

Answers (1)

SergeyA
SergeyA

Reputation: 62573

std::istream_iterators are different from 'regular' iterators. Stream iterators are single-pass. You can't use the same iterator twice - because every increment reads data from the stream, and data read from the stream is gone from the stream. But this is what you are trying to do:

vector<int> data(start, end);
for(auto it=start; it!=end; ++it)

Here iterator start is used twice - first to populate the vector, than to iterate over stream.

To fix your problem, iterate over vector in the loop, not the (used up) stream.

Upvotes: 3

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