Loop to process each line of text file in to one of three arrays

Question

I am trying to create a loop to split lines of a text file into different vectors where "persons" contains all lines, "v1" contains names, "v2" contains ages & "v3" contains pets. I have been able to push all lines to "persons" but how would I iterate over persons so that persons[0] = name, persons[1] = age, persons[2] = pet, persons[4] = name etc....? The code I have written gets stuck in an infinite loop.

#include <io>
#include <fstream>
#include <string>
#include <vector>

using namespace std;

int main()
{
    ifstream people("myfile.txt");
    vector<string> persons;
    vector<string> first_names;
    vector<float> ages;
    vector<string> pets;
    string l;
    float age;

    if(!people)
    {
        printf("fail");
        system("pause");
        return -1;
    }
    else
    {
        while(getline(people, l))
        {
            if (l.size() > 0)
            {
                people.push_back(l)
            }
        }
        int num = people.size();
        for (int i = 0; i < num; i + 3)
        {
            first_names.push_back(people[i]);     // These are the
            ages.push_back(stof(people[i+1]));    // lines created to
            pets.push_back(people[i+2]);          // push to seperate
        }                                         // arrays.
        return 0
    }
}

Text file example

Bob
25.5
Snake
Kerry
29.5
Dog

Answer 1

This is wrong:

 for (int i = 0; i < num; i + 3)

It should be

for (int i = 0; i < num; i += 3)

otherwise i will always be 0 and never more than num-1.