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1. What does this program print? ``

cpp
#include <iostream>
#include <vector>

int main() {
    std::vector<int> v = {1, 2, 3};
    for (int x : v) {
        x *= 2;
    }
    for (auto& x : v) {
        x += 10;
    }
    for (int x : v) {
        std::cout << x << ' ';
    }
    std::cout << '\n';
}

``

1 2 32 4 611 12 1312 14 16

2. The program below reads numbers from standard input. The input is 4, then 6, then 9, then -1, each on its own line. What does it print? ``

cpp
#include <iostream>

int main() {
    const int sentinel = -1;
    int x = 0;
    int total = 0;
    std::cin >> x;
    while (x != sentinel) {
        total += x;
        std::cin >> x;
    }
    std::cout << total << '\n';
}

``

1819280

3. The program below has a bug. What is it? ``

cpp
#include <iostream>

int main() {
    int arr[] = {1, 2, 3};
    int* p = arr;
    for (int x : p) {
        std::cout << x << '\n';
    }
}

``

arr needs an explicit size, such as arr[3]Nothing is wrong: the loop prints 1, 2 and 3 on separate linesThe loop should start at p + 1, because the first element is skippedA pointer is not a range, because it does not know where the array ends, so loop over arr itself

4. The input is 5, then 7, then -1. The program prints 11, but the correct total is 12. What is the bug? ``

cpp
#include <iostream>

int main() {
    const int sentinel = -1;
    int score = 0;
    int total = 0;
    do {
        std::cin >> score;
        total += score;
    } while (score != sentinel);
    std::cout << "total: " << total << '\n';
}

``

The sentinel is added to total before the check sees it, so the total is 1 too lowThe sentinel is never read, so the loop runs foreverThe check should be score >= sentinel, which stops the loop earlierThe total must start at -1 so that the sentinel cancels out

5. In a sentinel loop that divides an integer total by an integer count, what happens if the very first value read is the sentinel and the count check is missing?

The average is printed as 0The loop runs foreverThe program divides by zero and stops, with exit code 136 on this machineThe sentinel is averaged as -1

Iteration forms