CODEWITHSUNDEEP
c++visual-c++iterator
Shahrooz
Shahrooz

Reputation: 330

How to get a vector of strings from input?

I'm trying to get a vector of string from input to create a graph , but i don't know why in middle my code it crashes. please help me fix it. I use Visual Studio.

#include <iostream>
#include <vector>
#include <iterator>

void main(void)
{
    {
        using namespace std;
        int8_t n{ 0 };
        cout << "enter the size of graph : ";
        cin >> n;
        vector<string> graph(n);
        string connectionsWith;
        vector<string>::iterator i;
        string::iterator e;
        int p{ 0 };
        for (i = graph.begin(); i != graph.end(); ++i)
        {
            cout << '\n' << "enter the vertices that are connected to " << p << " : ";
            cin >> connectionsWith;
            graph.push_back(connectionsWith);
            p++;
        }
        p = 0;
        for (i = graph.begin(); i != graph.end(); ++i)
        {
            cout << p << " is connected to " << *i;
            p++;
        }
    }
}

Upvotes: 0

Views: 152

Answers (2)

programmer 05
programmer 05

Reputation: 74

life_steal pointed out the problem. I would like to add few information and other way to solve the problem. 

int8_t n{ 0 }; 

vector<string> graph(n); // Here initialization happening with ASCII. If input is "1" then it would be "49". Consider changing int8_t to int if you unaware of that. 

graph.push_back(connectionsWith); //Instead of this line Use: *i = connectionsWith; it directly assign the value.

Upvotes: 0

life_steal
life_steal

Reputation: 55

In your constructor of graph, you allocate n string. Inside the loop you add on top of the constructed n strings, n more strings via push back. That potentially invalidates your iterators, as ChrisMM said, also not the most efficient way to implement such a scenario.

So as a solution, instead of 

vector<string> graph(n);

do

vector<string> graph;
graph.reserve(n);

and iterate over the index, e.g. from 0 to n, and push back.

Especially in the first loop you are not dereferencing the iterator at all, which suggests that using index based loop would show your intent better.

Upvotes: 2

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