Error: no match for 'operator+' (operand types are 'std::__cxx11::list<int>' and 'int')|

Question

I'm trying to take an even integer array and odd integer list, and then try to merge them in a vector, using the merge algorithm available in STL of C++. The task requires specifically to use the merge algorithm, and I'm getting stuck in error at line 43 , right of which I've commented that that's the error point.

#include <iostream>
#include <algorithm>
#include <functional>
#include <cstring>
#include <vector>
#include <list>
#include <cstdlib>
using namespace std;
void display(list<int>&l){
    list<int>::iterator p;
    for(p=l.begin();p!=l.end();++p){
        cout<<*p<<", ";
    }
    cout<<"\n";
}
void display(int arr[6]){
     for(int i=0;i<6;i++){
        cout<<arr[i]<<" ";
     }
     cout<<"\n";
}
int main()
{
    int inp;
    int even_arr[6];
    list<int> odd_list(6);
    cout<<"Enter even numbers: ";
    for(int i=0;i<6;i++){
        cin>>even_arr[i];
    }
    display(even_arr);
    list<int>::iterator p;
    cout<<"\nEnter odd numbers: ";
    for(p=odd_list.begin();p!=odd_list.end();++p){
        cin>>inp;
        *p = inp;
    }
    display(odd_list);

    vector<int> vec1(12);
    list<int>::iterator itr=odd_list.begin();
    int *ptr=even_arr;
    merge(even_arr,even_arr+6,odd_list,odd_list+6,vec1);   //ERROR LINE

    return 0;
}

Answer 1

You can't add something to a std::list like you can do with arrays. Also it's better to be explicit about iterators and use std::end to get the past-the-end-iterator, since you want to use the whole array anyway.

Also std::merge() expects iterators but the last parameter is vec1 , which is a std::vector . The correct version would be:

merge(begin(even_arr), end(even_arr),
      begin(odd_list), end(odd_list),
      begin(vec1));

I omitted std:: to improve readability.

Use of std::begin over odd_list.begin() (and similar) is debatable and up to personal preference.