Frequency and top-k

Questions 1 to 5 of 8

1. 1. What does this program print? ``cpp #include <iostream> #include <map> int main() { std::map<int, int> freq; for (int x : {3, 1, 3, 2, 3, 1}) ++freq[x]; std::cout << freq[7] << ' ' << freq.size() << '\n'; } ``

   3 31 30 30 4
2. 2. What does this program print? ``cpp #include <functional> #include <iostream> #include <queue> #include <vector> int main() { std::priority_queue<int, std::vector<int>, std::greater<int>> heap; for (int x : {42, 7, 19}) heap.push(x); heap.pop(); std::cout << heap.top() << ' ' << heap.size() << '\n'; } ``

   19 27 219 342 3
3. 3. Which statements about the two-sum walk in lesson 10 are correct? Pick all that apply.

   Pick every answer that is true.

   It reads the input once, with one lookup per valueIt stores the current value before it looks for the partnerIt looks for the partner before it stores the current valueIt returns the two stored positions, not the two values
4. 4. The heap already holds k values, and a new value x arrives that beats the weakest value in the heap. Put the steps in the order the loop runs them.

   Use the arrows to put the steps in order.

   1. 1.Compare x with heap.top()↑↓
   2. 2.Call pop() to remove the weakest value↑↓
   3. 3.Call push(x) to store the new value↑↓
   4. 4.Check whether heap.size() is less than k↑↓
5. 5. In C++, what does seen[need] do when need is not already a key in the map seen?

   It returns end() and leaves the map unchangedIt inserts need with the value 0 and returns that 0It throws std::out_of_rangeIt returns -1 and leaves the map unchanged