Common C++ Code

Question 1

define a function template

Answer 1

template <typename>
T add(T a, T b) {
return a + b;
}</typename>

Question 2

define a class template

Answer 2

template <typename>
class Box {
public:
T value;
};</typename>

Question 3

initialize a bool

Answer 3

bool flag{};

Question 4

initialize a bool with value

Answer 4

bool flag{true};

Question 5

initialize a char

Answer 5

char c{};

Question 6

initialize a char with value

Answer 6

char c{‘a’};

Question 7

initialize an int

Answer 7

int x{};

Question 8

initialize an int with value

Answer 8

int x{42};

Question 9

initialize a long

Answer 9

long x{};

Question 10

initialize a long with value

Answer 10

long x{100000L};

Question 11

initialize a double

Answer 11

double d{};

Question 12

initialize a double with value

Answer 12

double d{3.14};

Question 13

initialize a float

Answer 13

float f{};

Question 14

initialize a float with value

Answer 14

float f{55.5f};

Question 15

initialize an int32_t

Answer 15

int32_t x{};

Question 16

initialize an int32_t with value

Answer 16

int32_t x{123};

Question 17

initialize a uint32_t

Answer 17

uint32_t x{};

Question 18

initialize a uint32_t with value

Answer 18

uint32_t x{100u};

Question 19

initialize a size_t

Answer 19

size_t c{};

Question 20

initialize a size_t with value

Answer 20

size_t c{10};

Question 21

initialize an empty string

Answer 21

std::string s{};

Question 22

initialize a string with value

Answer 22

std::string s{“hello”};

Question 23

get length of a string

Answer 23

size_t len = s.length();

Question 24

initialize an empty vector

Answer 24

std::vector<int> v{};</int>

Question 25

initialize a vector with values

Answer 25

std::vector v = {1, 2, 3};

Question 26

add value to a vector

Answer 26

v.push_back(4);

Question 27

find a value in a vector

Answer 27

auto it = std::find(v.begin(), v.end(), 2);

Question 28

initialize an empty stack

Answer 28

std::stack s{};

Question 29

add value to a stack

Answer 29

s.push(2);

Question 30

remove value from a stack

Answer 30

s.pop();

Question 31

peek at value in stack

Answer 31

auto top = s.top();

Question 32

initialize an empty queue

Answer 32

std::queue q{};

Question 33

add value to a queue

Answer 33

q.push(2);

Question 34

remove value from a queue

Answer 34

q.pop();

Question 35

peek at value at the front of a queue

Answer 35

auto f = q.front();

Question 36

peek at value at the back of a queue

Answer 36

auto b = q.back();

Question 37

initialize an empty priority queue (max heap)

Answer 37

std::priority_queue pq;

Question 38

initialize an empty priority queue (min heap)

Answer 38

std::priority_queue, std::greater> pq;

Question 39

add a value to a priority queue

Answer 39

pq.push(5);

Question 40

remove a value from the priority queue

Answer 40

pq.pop();

Question 41

peek at value in a priority queue

Answer 41

auto top = pq.top();

Question 42

initialize an empty doubly ended queue

Answer 42

std::deque dq{};

Question 43

initialize a doubly ended queue with values

Answer 43

std::deque dq{1, 2, 3};

Question 44

add a value to front of doubly ended queue

Answer 44

dq.push_front(0);

Question 45

add a value to back of doubly ended queue

Answer 45

dq.push_back(0);

Question 46

remove a value from front of doubly ended queue

Answer 46

dq.pop_front();

Question 47

remove a value from back of doubly ended queue

Answer 47

dq.pop_back();

Question 48

peek at front value of doubly ended queue

Answer 48

auto f = dq.front();

Question 49

peek at back value of doubly ended queue

Answer 49

auto b = dq.back();

Question 50

initialize an empty list

Answer 50

std::list l{};

Question 51

initialize a list with values

Answer 51

std::list l{1, 2, 3};

Question 52

add a value to front of list

Answer 52

l.push_front(0);

Question 53

add a value to back of list

Answer 53

l.push_back(0);

Question 54

remove value from front of list

Answer 54

l.pop_front();

Question 55

remove value from back of list

Answer 55

l.pop_back();

Question 56

peek at value in front of list

Answer 56

auto f = l.front();

Question 57

peek at value in back of list

Answer 57

auto b = l.back();

Question 58

initialize an empty pair

Answer 58

std::pair p{};

Question 59

initialize a pair with values

Answer 59

std::pair p{1, 'a'};

Question 60

initialize an empty tuple

Answer 60

std::tuple tup{};

Question 61

initialize a tuple with values

Answer 61

std::tuple tup{1, 'a', "hello"}

Question 62

initialize an empty set

Answer 62

std::unordered_set s{};

Question 63

initialize a set with values

Answer 63

std::unordered_set s{1, 2};

Question 64

add a value to a set

Answer 64

s.insert(3);

Question 65

find a value in a set

Answer 65

auto it = s.find(2);

Question 66

initialize an empty map

Answer 66

std::unordered_map m{};

Question 67

initialize a map with values

Answer 67

std::unordered_map m = {{1, "one"}, {2, "two"}};

Question 68

add a value to a map (with overwrite)

Answer 68

m[3] = "three";

Question 69

add a value to a map (no overwrite)

Answer 69

auto bool = m.emplace(3, "three").second;

Question 70

find a value in a map

Answer 70

auto it = m.find(1);

Question 71

initialize an empty variant

Answer 71

std::variant v{};

Question 72

create a variant type

Answer 72

using MyVariant = std::variant;

Question 73

set the value of a variant

Answer 73

myVariant = "hello";

Question 74

access a value of a variant

Answer 74

auto val = std::get(myVariant);

Question 75

move a string

Answer 75

std::string s2{std::move(s1)};

Question 76

pass a string by value

Answer 76

auto process(std::string s) -> void;

Question 77

pass a string by lvalue reference

Answer 77

auto process(std::string& s) -> void;

Question 78

pass a string by rvalue reference

Answer 78

auto process(std::string&& s) -> void;

Question 79

pass a string by read only reference

Answer 79

auto process(const std::string& s) -> void;

Question 80

create a unique pointer with value

Answer 80

auto up = std::make_unique(10);

Question 81

create a shared pointer with value

Answer 81

auto sp = std::make_shared(10);

Question 82

create a weak pointer from a shared pointer

Answer 82

std::weak_ptr wp = sp;

Question 83

cast a double in an int

Answer 83

double d = 3.7; int x = static_cast(d); // 3

Question 84

create a joinable thread

Answer 84

std::thread t([] { // work }); t.join();

Question 85

create a background thread

Answer 85

std::thread([] { // background work }).detach();

Question 86

use a mutex to protect a private member variable

Answer 86

{ std::lock_guard lock(mut); mValue++; }

Question 87

set an atomic bool

Answer 87

std::atomic flag{false}; flag.store(true);

Question 88

get the value of an atomic bool

Answer 88

bool value = flag.load();

Question 89

use a condition variable to wait

Answer 89

std::condition_variable cv; bool ready = false; std::unique_lock lock(m); cv.wait(lock, [] { return ready; });

Question 90

notify with a condition variable

Answer 90

{ std::lock_guard lock(m); ready = true; } cv.notify_one();

Question 91

find the max between two values

Answer 91

auto max = std::max(a, b);

Question 92

find the min between two values

Answer 92

auto min = std::min(a, b);

Question 93

check if char is a number

Answer 93

isdigit(c);

Question 94

check if char is a letter

Answer 94

isalpha(c);

Question 95

make char upper case

Answer 95

toupper(c);

Question 96

make char lower case

Answer 96

tolower(c);

Question 97

convert string to number

Answer 97

std::stoi("123");