Iterators

[Titanius]

This question is about iterators. I declare an iterator in a code and use it for printing some conatiner class object like a list for example. Then I change the list by moving its first element to the back. Next I want to print the modified list object again using an iterator, do I need to declare a new iterator?

[MrHutch]

Nope, you can reuse it.

#include <iostream>
#include <vector>
#include <ctime>
#include <algorithm>

int main(int argc, const char* argv[])
{
   std::vector<int> myVector;
   srand(time(NULL));
   
   for (int i=0; i < 10; ++i)
   {
      myVector.push_back(rand() % 100 + 1);
   }	

   std::vector<int>::iterator iter;
   
   std::cout << "Unsorted: ";
   for (iter = myVector.begin(); iter != myVector.end(); ++iter)
   {
      std::cout <<  "\t" << *iter;
   }
   std::cout << std::endl;
   
   std::sort(myVector.begin(), myVector.end());
   
   std::cout << "Sorted: ";
   for (iter = myVector.begin(); iter != myVector.end(); ++iter)
   {
      std::cout <<  "\t" << *iter;
   }
   std::cout << std::endl;
   
   return 0;
}

[Titanius]

Ok, but what about here:

#include <list>
#include <iostream>

using namespace std;

int main()
{
	list <int> A;//created two lists
	list <int> B;
	int i,j;
	cin>>i;
	while(i>0) {
		A.push_back(i);
		cin>>i;
	}/
	cin>>j;
	while(j>0) {
		B.push_front(j);
		cin>>j;
	}
	list<int>::const_iterator liter1=A.begin();
	list<int>::const_iterator liter2=B.begin();
	for(liter1=A.begin(); liter1!=A.end(); ++liter1) {
		cout<<*liter1<<" ";
	}
	cout<<endl;
	for(liter2=B.begin(); liter2!=B.end(); ++liter2) {
		cout<<*liter2<<" ";
	}
	cout<<endl<<endl;//empty line
	A.push_back(A.front());
	A.pop_front();
	B.push_back(B.front());
	B.pop_front();
	//list<int>::const_iterator liter3=A.begin();
	//list<int>::const_iterator liter4=B.begin();/
	while (liter1 != A.end()) {
		if(liter1 == A.begin()) {
			cout << *liter1;
		} else {
			cout <<","<< *liter1;
		}
		++liter1;
	}
	cout<<endl;
	
	while (liter2 != B.end()) {
		if(liter2 == B.begin()) {
			cout << *liter4;
		} else {
			cout <<","<< *liter2;
		}
		++liter2;
	}
	return 0;
}

If I run it , in the place where I used the iterators second time the code doesnt print what its supposed to print, it prints empty lines, why is that happening?

[MrHutch]

You never reset your iterators to the beginning of the container.

After pushing and popping, you want something like this prior to your while loops:

liter1 = A.begin();
liter2 = B.begin();