#include <algorithm>#include <array>#include <cassert>#include <complex>#include <iostream>#include <iterator> int main(){constexprstd::array v{1,2,3,4,4,3,7,8,9,10};std::cout<<"v: ";std::copy(v.cbegin(), v.cend(),std::ostream_iterator<int>(std::cout," "));std::cout<<'\n'; // Determine how many integers match a target value.for(constint target:{3,4,5}){constint num_items= std::count(v.cbegin(), v.cend(), target);std::cout<<"number: "<< target<<", count: "<< num_items<<'\n';} // Use a lambda expression to count elements divisible by 4.int count_div4= std::count_if(v.begin(), v.end(),[](int i){return i%4==0;});std::cout<<"numbers divisible by four: "<< count_div4<<'\n'; // A simplified version of `distance` with O(N) complexity:auto distance=[](auto first,auto last){return std::count_if(first, last,[](auto){returntrue;});};    static_assert(distance(v.begin(), v.end())==10); std::array<std::complex<double>,3> nums{{{4,2},{1,3},{4,2}}};#ifdef __cpp_lib_algorithm_default_value_type// T gets deduced making list-initialization possibleauto c= std::count(nums.cbegin(), nums.cend(),{4,2});#elseauto c= std::count(nums.cbegin(), nums.cend(),std::complex<double>{4,2});#endifassert(c==2);}

v: 1 2 3 4 4 3 7 8 9 10number: 3, count: 2number: 4, count: 2number: 5, count: 0numbers divisible by four: 3