GCC中使用hash_map

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GCC中使用hash_map

hash_map就是利用hash表实现的一个map，在查找是具有更快的效率，前提是你使用了适当的hash函数。hash_map不是STL中的一部分，但大多数C/c++的编译器都提供了这个容器。GCC也不例外，我在winds下使用的IDE是code blocks，它使用的编译器就是GCC。因为hash_map不是STL中的一部分，所以使用起来也不是很异样。下面的是我搜索到的一些资料： 【1】 http://zitronensaft.blogspot.com/2008/02/using-hashmap-on-gcc.html Using hash_map on GCC

If you have tried to use some STL containers with GCC, such as hash_map:

// error: hash_map: No such file or directory
#include <hash_map>

int main ()
{

// error: ‘hash_map’ is not a member of ‘std’
std ::hash_map <int ,int > hm ;

return 0 ;
}

Then you have realized that the code above does not compile. That's because on GCC, hash_map is not regarded as a standard container, but rather as a extension included in the __gnu_cxx namespace. In order to use hash_map and other extended containers with a minimum impact in your code (which is very important if it's intended to be cross-platform), you can use the following solution:

#ifdef __GNUC__
#include <ext/hash_map>
#else
#include <hash_map>
#endif


namespace std
{
using namespace __gnu_cxx ;
}

int main ()
{

std ::hash_map <int ,int > hm ;

return 0 ;
}

Hope that helps.