容器迭代器

容器迭代器

iterator：普通正向迭代器

• 可以读取

• 可以修改

  int main()
  {
        
        
      vector<int> vec;
      for (int i = 0; i < 20; i++)
      {
        
        
          vec.push_back(rand() % 100 + 1);
      }
      auto it = vec.begin();
      for ( ;it != vec.end();it++ )
      {
        
        
          if (*it % 2 == 0)
          {
        
        
              *it = 0;
          }
        
      }
      for (int val : vec)
          cout << val << " ";
      cout << endl;
      return 0;
  }
  

const_iterator:常量迭代器

const_iterator 继承自iterator

• 只读

• 不写

  int main()
  {
        
        
      vector<int> vec;
      for (int i = 0; i < 20; i++)
      {
        
        
          vec.push_back(rand() % 100 + 1);
      }
      vector<int>::const_iterator it = vec.begin();
  
      for ( ;it != vec.end();it++ )
      {
        
        
          if (*it % 2 == 0)
          {
        
        
              cout << *it << " ";
          }     
      }
      cout << endl;
      return 0;
  }
  
  

reverse_iterator 反向迭代器

反向遍历容器的元素

int main()
{
    
    
    vector<int> vec;
    for (int i = 0; i < 20; i++)
    {
    
    
        vec.push_back(rand() % 100 + 1);
    }
    vector<int>::const_iterator it = vec.begin();

    for ( ;it != vec.end();it++ )
    {
    
    
        cout << *it << " ";     
    }
    cout << endl;
    vector<int>::reverse_iterator rit = vec.rbegin();

    for (; rit != vec.rend(); rit++)
    {
    
    
        cout << *rit << " ";
    }
    cout << endl;
 
    return 0;
}

const_reverse_iterator 常量反向迭代器

• 反向遍历
• 只支持读，不能写