Function returning iterator to vector

Question

what is the best way of returning an iterator for the below code?In the below code it is not giving correct output for this line

cout<<*p<<endl;

#include<iostream>
#include<vector>
using namespace std;
vector <int> :: iterator int_begin(vector <int> V);
int main()
{
  vector <int> V;
  V.push_back(3);
  V.push_back(1);
  vector <int> :: iterator p=int_begin(V);
  cout<<*p<<endl;
  return 0;
}
vector <int> :: iterator int_begin(vector <int> V)
{
  cout<<*V.begin()<<endl;
  return V.begin();
}

You're returning an iterator of a temporary vector.

mljli
– mljli

2018-05-28 05:03:16 +00:00
Commented May 28, 2018 at 5:03 — mljli
– mljli, Commented May 28, 2018 at 5:03

R Sahu · Accepted Answer · 2018-05-28 05:12:51Z

3

You are passing the object by value to int_begin(). What you get back is an iterator to a std::vector that does not live past the function call. Hence, in the calling function, the iterator is invalid.

Pass the object by reference.

vector <int> :: iterator int_begin(vector <int>& V) // Passed by reference
{
  cout<<*V.begin()<<endl;
  return V.begin();
}

edited May 28, 2018 at 5:12

answered May 28, 2018 at 5:06

R Sahu

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1 Comment

R Sahu Over a year ago

@BODAPATINIRUPAMASAI, you are welcome. Glad I was able to help.

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