Multi-key and frequency order

Questions 1 to 5 of 8

1. 1. Staff rows must be grouped by department, with names in A to Z order inside each department. Which two-pass method gives that result?

   Stable sort by department first, then stable sort by nameStable sort by name first, then stable sort by departmentstd::sort by department, then std::sort by nameOne stable sort by name, with no second pass
2. 2. In a frequency comparator, why does the lesson read counts with count.at(a) instead of count[a]?

   at only reads the table and throws if the key is missing, while [] would add a zero entry during the sortat is faster than [] because it returns a copy of the count[] does not compile on a std::map, so at is the only choiceat makes the comparator sort in descending order by default
3. 3. Predict the output of this program. ``cpp #include <algorithm> #include <iostream> #include <map> #include <vector> int main() { std::vector<int> nums{7, 3, 7, 1, 3, 7, 2}; std::map<int, int> count; for (int x : nums) { ++count[x]; } std::sort(nums.begin(), nums.end(), [&count](int a, int b) { if (count.at(a) != count.at(b)) { return count.at(a) > count.at(b); } return a < b; }); for (int x : nums) std::cout << x << ' '; std::cout << '\n'; } ``

   3 3 7 7 7 1 27 7 7 3 3 2 17 7 7 3 3 1 27 7 7 1 2 3 3
4. 4. Predict the output of this program. ``cpp #include <algorithm> #include <iostream> #include <string> #include <vector> int main() { std::vector<std::string> words{"pear", "fig", "kiwi", "apple", "lime"}; std::sort(words.begin(), words.end(), [](const std::string& a, const std::string& b) { if (a.size() != b.size()) return a.size() < b.size(); return a < b; }); for (const std::string& w : words) std::cout << w << ' '; std::cout << '\n'; } ``

   apple fig kiwi lime pearfig apple kiwi lime pearkiwi lime pear fig applefig kiwi lime pear apple
5. 5. Predict the output of this program. ``cpp #include <algorithm> #include <iostream> #include <string> #include <vector> struct Staff { std::string dept; std::string name; int salary; }; int main() { std::vector<Staff> rows{ {"it", "Kiran", 61000}, {"sales", "Priya", 52000}, {"it", "Divya", 61000}, {"it", "Arjun", 70000}, {"sales", "Anand", 48000}, }; std::sort(rows.begin(), rows.end(), [](const Staff& a, const Staff& b) { if (a.dept != b.dept) return a.dept < b.dept; if (a.salary != b.salary) return a.salary > b.salary; return a.name < b.name; }); for (const Staff& s : rows) std::cout << s.name << ' '; std::cout << '\n'; } ``

   Arjun Divya Kiran Priya AnandArjun Kiran Divya Priya AnandDivya Kiran Arjun Anand PriyaAnand Arjun Divya Kiran Priya