3.4 introduction to the iterator

1. Each container type defines its own iterator type

Vector <int>: iterator ITER;

2. Begin () returns the iterator pointing to the first element.

End () returns the iterator pointing to the last and next element.

3. Use * ITER to unreference the iterator

4. The const_iterator type can be changed by itself. However, the value of the object to which it points cannot be changed.

5. // an iterator that cannot write Elements

Vector <int>: const_iterator ITER;

// An iterator whose value cannot change

Const vector <int> iterator ITER;

6.

Code:

2. # Include <iostream>
4. # Include <vector>
6. Using NamespaceSTD;
8. IntMain ()
10. {
12. IntReadin = 0;
14. Vector <Int> Ivec;
16. Cout <"Input numbers :"<Endl;
18. While(CIN> readin)
20. {
22. Ivec. push_back (readin );
24. }
26. If(Ivec. Size () = 0)
28. {
30. Cout <"No number Iput! "<Endl;
32. Return0;
34. }
36. Vector <Int>:: Iterator iter = ivec. Begin ();
38. For(; ITER <ivec. End ()-1; iter = ITER + 2)
40. {
42. Cout <* ITER + * (ITER + 1) <"";
44. }
46. Cout <Endl;
48. If(ITER! = Ivec. End ())
50. {
52. Cout <"A number was not calculated :"<* (Ivec. End ()-1 );
54. }
56. }

7. Arithmetic Operations of the iterator:

ITER + N; ITER-N;

Iter1-iter2; // calculate the distance between two iterators, which is the signed type of different_type

Any operation to change the length of a vector will invalidate the iterator.