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C++ Algorithm Functions copy_n()C++ Algorithm copy_n() function specifies the number of elements to be copied into the new container. The function is used to copy n elements of the container [first,last) into a different container starting from result. Syntaxtemplate<class InputIterator, class Size, class OutputIterator> OutputIterator copy_n(InputIterator first, Size n, OutputIterator result); Parameterfirst: It is an input iterator to the first element of the range, where the element itself is included in the range. last: It is an input iterator to the last element of the range, where the element itself is not included in the range. result: It is an output iterator to the first element of the new container in which the elements are copied. Return valueAn iterator to the last element of the new range beginning with result is returned. Example 1#include<iostream> #include<algorithm> #include<vector> using namespace std; int main() { vector<int> u1 = {2,6,8,4,9,4}; vector<int> u2(6); vector<int> u3(6); copy(u1.begin(), u1.begin()+3, u2.begin()); cout<<"The new vector with copy contains:"; for(int k=0; k<u2.size(); k++) cout<<u2[k]<<" "; copy_n(u1.begin(),4,u3.begin()); cout<<"\n"; cout<<"The new vector using copy_n contains:"; for(int m=0; m<u3.size(); m++) cout<<u3[m]<<" "; } Output: The new vector with copy contains: 2 6 8 0 0 0 The new vector using copy_n contains:2 6 8 4 0 0 Example 2#include<iostream> #include<algorithm> #include<vector> using namespace std; int main() { int newints[]={15,25,35,45,55,65,75}; std::vector<int> newvector; newvector.resize(7); std::copy_n(newints,7,newvector.begin()); std::cout<<"newvector contains:"; for(std::vector<int>::iterator ti= newvector.begin(); ti!=newvector.end();++ti) std::cout<<" "<<*ti; std::cout<<"\n"; return 0; } Output: newvector contains: 15 25 35 45 55 65 75 ComplexityThe complexity of the function is linear starting from the first element to the last one. Data racesUp to n elements of the container are accessed. ExceptionsThe function throws an exception if any of the container elements throws one.
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