std::advance 给迭代器增加指定偏移量

template <class InputIterator, class Distance>
  void advance (InputIterator& it, Distance n);
迭代器辅助函数。
使迭代器it偏移n，其中n为整数。

#include <iostream>     // std::cout
#include <iterator>     // std::advance
#include <list>         // std::list

int main () {
  std::list<int> mylist;
  for (int i=0; i<10; i++) mylist.push_back (i*10);

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

  std::advance (it,5);
  std::cout << "The sixth element in mylist is: " << *it << '
'; 

  std::advance (it,-1);
  std::cout << "The fifth element in mylist is: " << *it << '
'; 

  return 0;
}

The sixth element in mylist is: 50
The fifth element in mylist is: 40