如何在 C++ 中列表的单个位置插入多个不同的值？

Question

This code is from geeksforgeeks

list<int> list1; 

list1.assign(3, 2); 


list<int>::iterator it = list1.begin(); 

 
advance(it, 2); 


list1.insert(it, 5); 

 
cout << "The list after inserting"
     << " 1 element using insert() is : "; 
for (list<int>::iterator i = list1.begin(); 
     i != list1.end(); 
     i++) 
    cout << *i << " "; 

cout << endl; 


list1.insert(it, 2, 7); 

 
cout << "The list after inserting"
     << " multiple elements "
     << "using insert() is : "; 

for (list<int>::iterator i = list1.begin(); 
     i != list1.end(); 
     i++) 
    cout << *i << " "; 

cout << endl; 

It shows the output like this:-

   The list after inserting 1 element using insert() is : 2 2 5 2 
   The list after inserting multiple elements using insert() is: 2 2 5 7 7 2

So, I want to add different values in a single position than the duplication of the same value. Is that even possible? for ex- inserting 1,3,7 in 3rd position of the list.

Answer 1

Check the reference .

You can use one of insert() :

template< class InputIt >
void insert( iterator pos, InputIt first, InputIt last);            (until C++11)

template< class InputIt >
iterator insert( const_iterator pos, InputIt first, InputIt last ); (since C++11)

Example:

#include <iostream>
#include <vector>
#include <list>

int main(void) {
    std::list<int> list1 = {2, 2, 5, 2};
    std::vector<int> to_insert = {1, 3, 7};

    std::cout << "before insert:";
    for (int v : list1) std::cout << ' ' << v;
    std::cout << '\n';

    list1.insert(std::next(list1.begin(), 2), to_insert.begin(), to_insert.end());

    std::cout << " after insert:";
    for (int v : list1) std::cout << ' ' << v;
    std::cout << '\n';

    return 0;
}

Output:

before insert: 2 2 5 2
 after insert: 2 2 1 3 7 5 2