3.22.in

Some vector Operations Invalidate Iterators

In § 3.3.2 (p. 101) we noted that there are implications of the fact that vectors can grow dynamically.
We also noted that one such implication is that we cannot add elements to a vector inside a range for loop.
Another implication is that any operation, such as push_back, that changes the size of a vector potentially invalidates all iterators into that vector.
We'll explore how iterators become invalid in more detail in § 9.3.6 (p. 353).

Incrementing an iterator moves the iterator one element at a time.
All the library containers have iterators that support increment.
Similarly, we can use == and != to compare two valid iterators (§ 3.4, p. 106) into any of the library container types.