#include <iostream>

 #include <vector>

 #include <string>

 #define allocate_length 100000

 int main()

 {

     //allocator比new快的原因:分离分配和初始化这两个操作allocator少执行一步,new则一般执行两次(初始化和赋值);

     std::clock_t start = , end = ;

     start = clock();

     std::string *str1 = new std::string[allocate_length];

     auto str6=str1;

     for (int i = ; i < allocate_length; i++)

     {

         *str1++ = "Hello World";

     }

     delete []str6;

     end = clock();

     std::cout << (double(end - start) / CLOCKS_PER_SEC) << std::endl;

     start = clock();

     std::allocator<std::string> str_allocate;

     std::string *str3 = str_allocate.allocate(allocate_length); //分配20个string原始内存

     auto str4=str3;

     //方法一:使用默认构造

     for (int i = ; i < allocate_length; i++)

     {

         str_allocate.construct(str3++,"Hello World");

     }

     //方法二:使用allocator的伴随算法(分别是带n与不带)

     //其他算法:std::uninitialized_copy(iterator begin,iterator end,T value);

     //std::uninitialized_fill_n(str3,allocate_length,"Hello World");

     //str_allocate.destroy()调用对象的析构，但是内存还是由allocator控制，需要自己释放

     str_allocate.deallocate(str4,allocate_length);

     end = clock();

     std::cout << (double(end - start) / CLOCKS_PER_SEC) << std::endl;

     return ;

 }