Iterator function operation of iterator learning

Learning in this chapter Iterator Iterator function operation of , The specific functions are as follows ：

Defined in header file <iterator>
advance	Make the iterator advance a given distance ( Function templates )
distance	Returns the distance between two iterators ( Function templates )
begin	Start iterator ( Function templates )
end	End iterator ( Function templates )
next (C++11)	Make the iterator self augment ( Function templates )
prev (C++11)	Make the iterator subtract itself ( Function templates )

Code example 1

advance We know list The list can take the head element and the tail element , What if we want to take the intermediate element and operate , Because it doesn't have [i] There are no at(i) operation , So use advance Function can get any element in the middle , Specific examples are as follows ：

#include <iostream>
#include <iterator>
#include <list>

using namespace std;

int main()
{
    list<int> mylist{10,20,30,40,50,60,70,80,90,100};
    for(auto li = mylist.begin(); li != mylist.end(); ++li)
    {
        cout << *li << "\t";
    }
    cout << "\n";
    // Take the first place 5 Gewusu 
    list<int>::iterator it = mylist.begin();
    std::advance(it, 4);
    cout << "The five element in mylist is: " << *it << endl;

    list<int>::iterator it1 = mylist.begin();
    std::advance(it1, 6);
    cout << "The seven element in mylist is: " << *it1 << endl;
    *it1 = 90;
    for(auto li = mylist.begin(); li != mylist.end(); ++li)
    {
        cout << *li << "\t";
    }
    cout << "\n";
    cout << "Hello World!" << endl;
    return 0;
}

​

  Code example 2 distance Take the distance between two iterators

#include <iostream>
#include <iterator>
#include <vector>

using namespace std;

int main()
{
    list<int> mylist{10,20,30,40,50,60,70,80,90,100};
    std::list<int>::iterator first = mylist.begin();
    std::list<int>::iterator last = mylist.end();
    std::cout << "list   distance(first, last) = " << std::distance(first, last) << '\n';
    //std::cout << "list   distance(last, first) = " << std::distance(last, first) << '\n'; //list Out of commission 
    std::vector<int> vec{32, 15, 43, 25, 36};

    std::vector<int>::iterator vfirst = vec.begin();
    std::vector<int>::iterator vlast = vec.end();
    std::cout << "vector distance(first, last) = " << std::distance(vfirst, vlast) << '\n';
    std::cout << "vector distance(last, first) = " << std::distance(vlast, vfirst) << '\n';

    cout << "\n";
    cout << "Hello World!" << endl;
    return 0;
}

  Code example 3 begin Start iterator

#include <iostream>
#include <iterator>
#include <vector>

using namespace std;

int main()
{
    //3.begin
    std::vector<int> vec{32, 15, 43, 25, 36};
    std::vector<int>::iterator iter2 = vec.begin();
    // take vector The first 2 Elements 
    ++iter2;
    std::cout << "vector iter2 = " << *iter2 << '\n';

    cout << "Hello World!" << endl;
    return 0;
}

 

Code example 4 end End iterator

#include <iostream>
#include <iterator>
#include <vector>

using namespace std;

int main()
{
    std::vector<int> vec{32, 15, 43, 25, 36};
    // take vector The last element 
    std::vector<int>::iterator iter = vec.begin();
    while(iter != vec.end())
    {
        ++iter;
        if(iter == vec.end())
        {
            // Take the last element 
            --iter;
            std::cout << "vector iter = " << *iter << '\n';
            break;
        }
    }


    cout << "\n";
    cout << "Hello World!" << endl;
    return 0;
}