Iteration and counts

Questions 1 to 5 of 8

1. 1. A multiset holds the values 8, 8 and 9. What does ms.erase(8) do?

   It removes only the first 8It removes both 8s, so every element equal to 8 is goneIt removes the last 8 and keeps the firstIt does nothing, because the value appears more than once
2. 2. Why should a program not depend on the order of the items in an unordered_map loop?

   The standard makes no promise about that order, and it depends on the hash values and the bucket countIts keys are always stored in reverse insertion orderIt sorts keys only when they are numbersThe keys are sorted once the map holds 100 items
3. 3. Which function returns an iterator to the first element that is not less than a value, or end() if every element is smaller?

   upper_boundfindlower_boundcount
4. 4. In a range-based for loop over an unordered_map, calling erase on the current key and then letting the loop move on is safe, because the loop refreshes its iterator after each erase.

   True, because the loop refreshes its iterator after each eraseFalse, because the erased item's iterator is invalid and the loop's ++ step still uses it
5. 5. A counted map may keep a key whose count has dropped to 0, because size() counts only keys that still have stock.

   False, because size() counts every key, so a key left at 0 is still counted and the map is wrongTrue, because size() counts only keys with a count above 0