vector<int> x(3, 0);
vector<int>::iterator it;

it = x.begin();
x.insert(it, 5);

while(it != x.end())
{
   cout << *it << endl;
   ++it;
}

Ausgabe:

0
0
0
1207979854
196612
524628
5
0
0
0

erwartet hätte ich eher:

5
0
0
0

vector<int> x( 3, 0 );
vector<int>::iterator it;
x.insert( x.begin(), 5 ); 
it = x.begin();

while(it != x.end()) 
{ 
	cout << *it << endl; 
	++it;
}