c++ distance 和advance函数

 distance主要是用来求两个迭代器之间的元素个数。

template<class InputIterator>
  typename iterator_traits<InputIterator>::difference_type
    distance (InputIterator first, InputIterator last);

Return distance between iterators

Calculates the number of elements between first and last.

If i is a Random Access Iterator, the function uses operator- to calculate this. Otherwise, the function uses the increase operator (operator++) repeatedly.

 

advance函数增加迭代器。

template <class InputIterator, class Distance>
  void advance (InputIterator& i, Distance n);

Advance iterator

Advances the iterator i by n elements.

Distance：Distance is any numerical type able to represent distances between iterators of this type.

 

#include <iostream>
#include <iterator>
#include <list>
using namespace std;

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

  list<int>::iterator first = mylist.begin();
  list<int>::iterator last = mylist.end();

  cout << "The distance is: " << distance(first,last) << endl;//输出10
  
  list<int>::iterator it=mylist.begin();
  advance(it,5);
  cout<<*it; //输出50

  return 0;
}

深入：

http://www.cnblogs.com/woodfish1988/archive/2007/02/27/658498.html