stl中hash_map的使用
我采用如下方式定义一个结构体
struct POINT{
double x;
double y;
};
#include<hash_map>
using namespace stdext;

hash_map<int ,POINT> PtHash;
然后想通过hash_map的find函数查找当前点POINT是否与hashmap中的相等，该如何做呢？求指点，谢谢！

[解决办法]

C/C++ code

// hash_map_find.cpp// compile with: /EHsc#define _DEFINE_DEPRECATED_HASH_CLASSES 0#include <hash_map>#include <iostream>int main( ){   using namespace std;   using namespace stdext;   hash_map <int, int> hm1;   hash_map <int, int> :: const_iterator hm1_AcIter, hm1_RcIter;   typedef pair <int, int> Int_Pair;   hm1.insert ( Int_Pair ( 1, 10 ) );   hm1.insert ( Int_Pair ( 2, 20 ) );   hm1.insert ( Int_Pair ( 3, 30 ) );   hm1_RcIter = hm1.find( 2 );   cout << "The element of hash_map hm1 with a key of 2 is: "        << hm1_RcIter -> second << "." << endl;   // If no match is found for the key, end( ) is returned   hm1_RcIter = hm1.find( 4 );   if ( hm1_RcIter == hm1.end( ) )      cout << "The hash_map hm1 doesn't have an element "           << "with a key of 4." << endl;   else      cout << "The element of hash_map hm1 with a key of 4 is: "           << hm1_RcIter -> second << "." << endl;   // The element at a specific location in the hash_map can be found    // using a dereferenced iterator addressing the location   hm1_AcIter = hm1.end( );   hm1_AcIter--;   hm1_RcIter = hm1.find( hm1_AcIter -> first );   cout << "The element of hm1 with a key matching "        << "that of the last element is: "        << hm1_RcIter -> second << "." << endl;}   Copy Code The element of hash_map hm1 with a key of 2 is: 20.The hash_map hm1 doesn't have an element with a key of 4.The element of hm1 with a key matching that of the last element is: 30.
[解决办法]
你的key是int，却要找一个POINT，设计有问题，非要找的话，只能自己遍历来找。
map的key才是用来查找的。
[解决办法]
既然是map，当然要使用其高速查找的特性，如果你通过遍历去查找，当然也是能查找的，此时map容器就退化为vector了，甚至比vector效率还差。

每个容器都有自己的优点缺点，如果你非要用其弱点，那就本末倒置了。