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1. What does this program print? ``

cpp
#include <algorithm>
#include <iostream>
#include <vector>

int main() {
    std::vector<int> v = {3, 7, 7, 12, 18};
    auto it = std::ranges::lower_bound(v, 7);
    std::cout << (it - v.begin()) << '\n';
    auto it2 = std::ranges::lower_bound(v, 10);
    std::cout << *it2 << '\n';
}

``

0, then 72, then 181, then 121, then 7

2. What does this program print? ``

cpp
#include <algorithm>
#include <iostream>
#include <vector>

// Print every pair of values that adds up to target. Works on sorted input.
void print_pairs(const std::vector<int>& sorted, int target) {
    std::size_t lo = 0;
    std::size_t hi = sorted.size() - 1;
    while (lo < hi) {
        int sum = sorted[lo] + sorted[hi];
        if (sum == target) {
            std::cout << sorted[lo] << " + " << sorted[hi] << " = " << target << '\n';
            ++lo;
            --hi;
        } else if (sum < target) {
            ++lo;
        } else {
            --hi;
        }
    }
}

int main() {
    std::vector<int> v = {2, 9, 4, 7, 1, 8, 5};
    std::ranges::sort(v);
    print_pairs(v, 10);
}

``

1 + 9 = 10 only1 + 9 = 10, then 2 + 8 = 102 + 8 = 10, then 4 + 5 = 91 + 9 = 10, then 2 + 8 = 10, then 4 + 7 = 11

3. Complete the sentence. When no two neighbouring values in a list are equal, std::ranges::adjacent_find returns the ____ of the list.

Type your answer.

4. On an empty std::vector, sorted.size() - 1 wraps around to a huge number, because size() returns an ____ type. Fill in the blank.

Type your answer.

5. In a sorted list, why does checking only neighbouring pairs find the closest pair of values?

If a value sat between the closest pair, it would be at least as close to one of them, so the closest pair must be neighboursThe scan sorts the gaps first, so the smallest gap is always at the front of the listBinary search checks each neighbour and always returns the closest valueNeighbours in a sorted list always differ by exactly one, so the smallest gap is always one

Sort then search