std::remove, std::remove_if in c++

std :: vector <int> vec1 { 10, 20, 30, 30, 20, 10, 10, 20};     std :: vector <int> vec2 { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10};           // Print original vector     std :: cout << "Original vector : ";     for(int i=0; i < vec1.size(); i++)         std :: cout << " " << vec1[i];     std :: cout << "\n";       // Iterator that store the position of last element     std :: vector <int>::iterator pend;           // std ::remove function call     pend = std :: remove (vec1.begin(), vec1.end() , 20);           // Print the vector     std :: cout << "After remove : ";     for ( std :: vector<int> :: iterator p=vec1.begin(); p != pend; ++p)         std :: cout << ' ' << *p;     std :: cout << '\n';       // Print original vector     std :: cout << "\nOriginal vector : ";     for(int i=0; i < vec2.size(); i++)         std :: cout << " " << vec2[i];     std :: cout << "\n";       // std ::remove_if function call     pend = std :: remove_if (vec2.begin(), vec2.end() , IsOdd);           // Print the vector     std :: cout << "After remove_if : ";     for ( std :: vector<int> :: iterator q=vec2.begin(); q != pend; ++q)         std :: cout << ' ' << *q;     std :: cout << '\n';

Output:

Original vector :  10 20 30 30 20 10 10 20
After remove :  10 30 30 10 10

Original vector :  1 2 3 4 5 6 7 8 9 10
After remove_if :  2 4 6 8 10