Why use iterators

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1 对于Vector，迭代器跟索引差别不大

for ( int i=0; i < vecVector.size(); i++ ){..}
  
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for (auto iter = vecVector.begin(); iter != vecVector.end(); iter++){ ...}
  
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但是，仅仅可以对支持 operator[](std::size_t)的容器使用索引

2 但是在vector中删除、插入元素，迭代器比索引更加方便

some_iterator = some_vector.begin();while (some_iterator != some_vector.end()){    if (/* some condition */)    {        some_iterator = some_vector.erase(some_iterator);        // some_iterator now positioned at the element after the deleted element    }    else    {        if (/* some other condition */)        {            some_iterator = some_vector.insert(some_iterator, some_new_value);            // some_iterator now positioned at new element        }        ++some_iterator;    }}
  
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3 迭代器让你的代码更加通用
比如：

typedef std::vector<int> Container ;void doSomething(Container & p_aC){    for(Container::iterator it = p_aC.begin(), itEnd = p_aC.end(); it != itEnd; ++it)    {       int & i = *it ; // i is now a reference to the value iterated       // do something with "i"    }}
  
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如果，使用list替代上面的vector，那么迭代器的优势就显现出来了。

4 更重要的是，迭代器用于算法

copy(v.begin(), v.end(), l.begin());for (auto it = v.begin(); it != v.end(); ++it) {    // if the current index is needed:    auto i = std::distance(v.begin(), it);    // access element as *it    // any code including continue, break, return}
  
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5 迭代器更具有oop思想

6 模板编程

template <class Container>double product( const Container & container ){  Container::iterator i = container.begin();  double prod = 1;  while ( i != container.end() ) prod *= *i++;  return prod;}
  
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Iterators make your code more generic.

for_each + lambda

std::for_each(v.begin(), v.end(), [](T const& elem) {     // if the current index is needed:     auto i = &elem - &v[0];     // cannot continue, break or return out of the loop});
  
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