module 4

Question 1

Given int a[6] {1, 2, 3, 4, 5, 6}; use copy() to output each element of the array without using begin() and end()

Answer 1

copy(a, a + 6, ostream_iterator<int>(cout, " "));

Question 2

Given int a[6] {1, 2, 3, 4, 5, 6}; use copy() to output each element of the array using begin() and end()

Answer 2

copy(begin(a), end(a), ostream_iterator<int>(cout, " "));

Question 3

Non-mutating algorithms defined in <algorithm>

Answer 3

• for_each
• find
• find_if
• find_first_of
• adjacent_find
• count
• count_if
• mismatch
• equal
• search
• find_end
• search_n

Question 4

Mutating Algorithms defined in <algorithm>

Answer 4

• transform
• copy
• copy_if
• copy_backward
• swap
• iter_swap
• swap_ranges
• replace
• replace_if
• replace_copy
• replace_copy_if
• fill
• fill_n
• generate
• generate_n
• remove
• remove_if
• remove_copy
• remove_copy_if
• unique
• reverse
• reverese_copy
• rotate
• rotate_copy
• random_shuffle

Question 5

Sorting Algorithms defined in <algorithm>

Answer 5

• sort
• stable_sort
• partial_sort
• partial_sort_copy
• nth_element
• merge
• inplace_merge
• partition
• stable_partition

Question 6

set operations defined in <algorithm>

Answer 6

• includes
• set_union
• set_intersection
• set_difference
• set_symmetric_difference

Question 7

Heap (priority queue) operations defined in <algorithm>

Answer 7

• push_heap
• pop_heap
• make_heap
• sort_heap

Question 8

Searching Algorithms defined in <algorithm>

Answer 8

• binary_search
• lower_bound
• upper_bound
• equal_range

Question 9

Min and Max algorithms defined in <algorithm>

Answer 9

• min
• max
• min_element
• max_element
• lexicographical_compare

Question 10

Permutation algorithms defined in <algorithm>

Answer 10

• next_permutation
• prev_permutation

Question 11

Write a function called selection_sort() that takes two iterator pointer parameters, one to the beginning and one to the end.

#include <algorithm>

Answer 11

#include <algorithm>
using namespace std;

template<typename Iter>
void selection_sort(Iter begin, Iter end) {
    for (; begin != end; ++begin) {
        iter_swap(begin, min_element(begin, end));
    }
}

Question 12

Numeric Algorithms defined in <numeric>

Answer 12

• accumulate(beg, end, init)
• accumulate(beg, end, init, bin_function())
• inner_product
• partial_sum
• adjacent_difference
• iota

Question 13

Write a predicate function that that takes an int as a parameter and determines if a number in a vector<int> is less than 19, then use that function in a copy_if()

Answer 13

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

int main() {
  vector<int> a = {3, 6, 9, 12, 18, 21, 24, 27, 30};
  vector<int> b(a.size());
  auto endb = copy_if(begin(a), end(a), begin(b), [](int x){return x < 19;});
}

predicate functions are functions that return a bool

Question 14

Overload the function call operator() in struct Plus in order to execute the following code in main:

int main() {
    Plus<int> p;
    cout << p(2,3) << endl;             // 5
    
    Plus<string> p2;
    cout << p2("carrot","top") << endl; // carrottop
}

Answer 14

template<class T>
struct Plus {
    T operator()(const T& m, const T& n) {
        return m+n;
    }
};

Question 15

Output the contents of the following array a with a space between each value without using a loop.

int a[7] {1, 2, 3, 4, 5};

Answer 15

copy(begin(a), end(a), ostream_iterator(cout, " ")); 
// output -> 1 2 3 4 5 0 0 

Question 16

Copy the numbers from the following string into a vector without using a loop;

string s = "12 13 14 15 16 17";

Answer 16

    istringstream is(s);
    istream_iterator<int> b(is);
    istream_iterator<int> e;
    vector<int> a(b, e);

Question 17

Write a vector of the type function<int(int,int)>, three lamba functions to add to the vector, then run it against the following code:

template<class F>
void apply(F f) {
    cout << f(2,3) << endl;
}
int main() {
    vector<function<int(int,int)>> funs;
    // write lambda functions here
    for_each(funs.begin(), funs.end(), &apply<function<int(int,int)>>);
}

Answer 17

    funs.push_back([](int x, int y){return x + y;});
    funs.push_back([](int x, int y){return x * y;});
    funs.push_back([](int a, int b){return a - b;});

Question 18

Write a function, function<int(int)> addx(int) that returns a lambda function. Make the lambda function capture the addx() functions parameter.

Answer 18

function<int(int)> addx(int x) {
    return [x](int y)->int {return x+y;};
}

Question 19

Write a recursive lambda that executes the fibonacci sequence

Answer 19

function<int(int)> fib =
        [&fib](int n) {return n < 2 ? n : fib(n-1) + fib(n-2);};

Question 20

Lambda Capture Summary

Answer 20

• [] - the lambda cannot use any variables from the enclosing function
• [names] - names = a comma-separated list of names local to the enclosing function, their rvalues are copied into the lambda by default
• [&] - by reference capture list
• [=] - by value capture list
• [&, names] - a comma-separated list of names local to the enclosing function, they are passed by reference
• [=, names] - a comma-separated list of names local to the enclosing function, they are passed by reference

Question 21

Write a reverse iterator to print the following vector backwards:

vector<int> lyst = {1, 2, 3, 4, 5};

Answer 21

auto p = lyst.rbegin();
while (p != lyst.rend()) {
      cout << *p << endl;
      \++p;
}