For this iterator which of the following is correct? If correct what does the expression produce?

Question

Suppose we have the following definition:
```
vector vec;
// use push_back to put 10 values into vec here.
vector::iterator itr1, itr2,itr3;
itr1 = vec.begin();
itr2 = vec.begin() + 5;
itr3 = vec.end();
```

a) *iter1
b) itr2[3]
c) itr + 3
>>>there is no itr, Do you mean itr3?
d) itr – 3
e) itr3 – itr1 (if valid, what does this produce?)
>>You asked for what is produced for all of them in intro to question

Answer 1

All parts are correct.

Part a) is an expression that returns the first element in the vector. Part b) returns the middle + 3rd, i.e., the 8th element.
c) returns an iterator to the 8th element
d) returns an iterator to the (5-2)th element, that is, the 2nd element
e) Though not explicitly mentioned in the text, there is enough information there that the student should be able to deduce that this expression returns the number of elements between the front and the back of the vec.