Master C++ Interview Hotspots: From C++11 to C++20 New Features

In today’s competitive tech hiring market, C++ developers must master new language features to stand out; interviewers often test knowledge of C++11, C++14, C++17 and C++20 because they reveal a candidate’s ability to write modern, efficient code.

Part1 C++11 New Feature Hotspots

1.1 Auto type deduction and range‑based for loop

Using auto lets the compiler infer a variable’s type from its initializer:

auto x = 10; // int
auto str = "Hello"; // const char*

The range‑based for loop simplifies container traversal:

std::vector<int> numbers = {1,2,3,4,5};
for (auto num : numbers) {
    std::cout << num << " ";
}

1.3 nullptr keyword

nullptr

safely represents a null pointer, avoiding ambiguous overloads.

1.4 New cast operators

static_cast – compile‑time checked conversions.

dynamic_cast – safe down‑casting with runtime checks.

const_cast – removes constness.

reinterpret_cast – low‑level reinterpretation of bits.

1.5 Lambda expressions

Lambdas create anonymous functions; basic syntax:

[capture](params) -> return_type { body }

1.6 Move semantics and rvalue references

Move semantics transfer resource ownership, reducing copies; rvalue references ( &&) enable moves.

1.7 Initializer lists

Classes can initialize members directly:

class MyClass {
public:
    MyClass(int a, int b) : memberA(a), memberB(b) {}
private:
    int memberA;
    int memberB;
};

1.8 Type aliases with using

using myInt = int;
using IntVector = std::vector<int>;

1.9 Thread support library

#include <thread>
void printMessage() { std::cout << "Hello from thread!" << std::endl; }
int main() {
    std::thread t(printMessage);
    std::cout << "Hello from main thread!" << std::endl;
    t.join();
}

1.10 Smart pointers

std::unique_ptr

provides exclusive ownership; std::shared_ptr enables shared ownership with reference counting.

Part2 C++14 New Feature Hotspots

2.1 New features

Generic lambdas with auto parameters.

Return type deduction.

Auto in initializer lists.

Binary digit separators.

Extended constexpr functions.

Improved variadic templates.

Void‑returning lambdas.

2.2 auto usage and limits

Variables declared with auto must be initialized; it can deduce references and works with most types but not directly with arrays or function pointers.

2.3 Lambdas in C++14

Lambda syntax unchanged, but return type can be deduced automatically.

2.4 constexpr enhancements

Now allows loops, conditionals, and variable templates.

2.5 New standard library components

std::make_unique

std::integer_sequence

User‑defined literals

Extended generic lambdas

Variadic pack expansions std::experimental utilities (optional, any, string_view)

2.6 Variadic templates example

#include <iostream>
void printArgs() { std::cout << "All arguments printed." << std::endl; }

template<typename T, typename... Args>
void printArgs(T first, Args... args) {
    std::cout << "Argument: " << first << std::endl;
    printArgs(args...);
}

int main() { printArgs(1, "Hello", 3.14, 'A'); }

2.8 Raw string literals

const char* s = R"(Hello 
 World!)";
const char* s2 = R"###(This is a "quoted" string.)###";

2.9 std::make_unique and std::make_shared

auto up = std::make_unique<int>(42);
auto sp = std::make_shared<int>(42);

2.10 Uniform initialization syntax

int num{42};
auto val{3.14};
MyClass obj{5};
int empty{}; // zero‑initializes

Part3 C++17 New Feature Hotspots

3.1 Extended type deduction

auto

can be used for function return types, parameters and non‑static data members.

3.2 Structured bindings

#include <tuple>
std::tuple<int,std::string,double> t{1,"hi",2.5};
auto [i,s,d] = t;

3.3 if constexpr

Compile‑time conditional branching eliminates dead code.

3.4 Fold expressions

template<typename... Args> auto sum(Args... args) { return (args + ...); }

3.5 Expanded constexpr

constexpr int add(int a,int b){ return a+b; }
static_assert(add(5,7)==12);

3.6 Parallel algorithms

Algorithms like std::for_each have parallel overloads (e.g., std::for_each(std::execution::par, ...)).

3.7 Filesystem library

std::filesystem

provides portable path manipulation, file creation, deletion, and iteration.

Part4 C++20 New Feature Hotspots

4.1 Major additions

Concepts for template constraints.

Three‑way comparison operator <=>.

Init‑capture extensions for lambdas.

Coroutines with co_await, co_yield, co_return.

Modules to replace header inclusion.

Contracts (pre‑ and post‑conditions).

Ranges library for composable views. std::format for type‑safe formatting.

Digit separators using '.

4.2 Modules

Declare a module with export module name; and import with import name;. Interface files (.ixx) define exported symbols, and the compiler handles compile‑time linking.

4.3 Lambda improvements

Init‑capture allows initializing captured variables.

Implicit capture when parameter list is omitted. constexpr lambdas for compile‑time evaluation.

Template parameter deduction in lambdas.

4.4 Concepts

Concepts describe requirements on template arguments, providing clearer error messages and safer code.

4.5 Coroutines

Keywords co_await, co_yield, co_return. std::coroutine_traits and std::coroutine_handle for custom coroutine types.

Generators enable lazy sequence production.

4.6 Asynchronous support

Coroutines for lightweight async operations. std::jthread automatically joins on destruction.

Coroutine‑friendly timers and cooperative cancellation.

Atomic wait/notify for low‑level synchronization.

4.7 std::format changes

Type‑safe placeholders {} with optional indices.

Named arguments, alignment, width, precision options.

Custom formatters for user‑defined types.

4.8 New data structures and algorithms

Ranges library for composable view pipelines.

Three‑way comparison via operator<=>.

Calendar and time‑zone utilities. std::span, std::bit_span, std::slist containers.

Extended mathematical functions.