Practice Questions — Modern C++ Features (C++11 to C++20)

#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;

struct Student {
    string name;
    int marks;
    char grade;
};

int main() {
    vector<Student> students = {
        {"Arjun", 85, 'B'}, {"Priya", 92, 'A'},
        {"Kiran", 78, 'B'}, {"Neha", 92, 'A'}
    };
    sort(students.begin(), students.end(),
        [](const Student& a, const Student& b) {
            if (a.marks != b.marks) return a.marks > b.marks;
            return a.name < b.name;
        });
    for (const auto& [name, marks, grade] : students)
        cout << name << ": " << marks << " (" << grade << ")" << endl;
    return 0;
}

#include <iostream>
#include <functional>
#include <cmath>
using namespace std;

function<int(int)> makeOp(const string& op, int n) {
    if (op == "add")
        return [n](int x) { return x + n; };
    if (op == "multiply")
        return [n](int x) { return x * n; };
    if (op == "power")
        return [n](int x) { return (int)pow(x, n); };
    return [](int x) { return x; };
}

int main() {
    auto add5 = makeOp("add", 5);
    auto mul3 = makeOp("multiply", 3);
    auto pow2 = makeOp("power", 2);
    cout << "add5(10) = " << add5(10) << endl;
    cout << "mul3(10) = " << mul3(10) << endl;
    cout << "pow2(10) = " << pow2(10) << endl;
    return 0;
}

#include <iostream>
#include <array>
using namespace std;

constexpr long long factorial(int n) {
    long long result = 1;
    for (int i = 2; i <= n; i++)
        result *= i;
    return result;
}

template<size_t... Is>
constexpr auto makeFactTable(index_sequence<Is...>) {
    return array<long long, sizeof...(Is)>{factorial(Is)...};
}

constexpr auto factTable = makeFactTable(make_index_sequence<13>{});

int main() {
    for (int i = 0; i <= 12; i++)
        cout << i << "! = " << factTable[i] << endl;
    return 0;
}

#include <iostream>
#include <vector>
#include <algorithm>
#include <numeric>
using namespace std;

int main() {
    vector<int> v = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};

    // Step 1: Remove odd numbers
    v.erase(remove_if(v.begin(), v.end(), [](int x) { return x % 2 != 0; }), v.end());
    cout << "Even numbers: ";
    for (auto x : v) cout << x << " ";
    cout << endl;

    // Step 2: Square each element
    transform(v.begin(), v.end(), v.begin(), [](int x) { return x * x; });
    cout << "Squared: ";
    for (auto x : v) cout << x << " ";
    cout << endl;

    // Step 3: Sum
    auto sum = accumulate(v.begin(), v.end(), 0);
    cout << "Sum of squares: " << sum << endl;
    return 0;
}

#include <iostream>
#include <optional>
using namespace std;

optional<double> safeDivide(double a, double b) {
    if (b == 0) return nullopt;
    return a / b;
}

void printResult(double a, double b) {
    auto result = safeDivide(a, b);
    cout << a << " / " << b << " = ";
    if (result)
        cout << result.value() << endl;
    else
        cout << "error (division by zero)" << endl;
}

int main() {
    printResult(10, 3);
    printResult(10, 0);
    printResult(100, 4);
    return 0;
}

#include <iostream>
#include <vector>
#include <algorithm>
#include <concepts>
#include <string>
using namespace std;

template<typename C>
concept Sortable = requires(C c) {
    { c.begin() } -> input_or_output_iterator;
    { c.end() } -> input_or_output_iterator;
    requires totally_ordered<typename C::value_type>;
};

void sortAndPrint(Sortable auto& container) {
    sort(container.begin(), container.end());
    for (const auto& x : container) cout << x << " ";
    cout << endl;
}

int main() {
    vector<int> ints = {5, 3, 1};
    vector<string> strs = {"Kiran", "Arjun", "Priya"};
    vector<double> dbls = {3.14, 1.41, 2.72};
    sortAndPrint(ints);
    sortAndPrint(strs);
    sortAndPrint(dbls);
    return 0;
}