std:sort和字符串hash函数

class CStudent

{

public:

CStudent() {}

~CStudent() {}

bool operator<(const CStudent &stu) const

{

return num > stu.num;

}

int num;

};

struct cmp

{
bool operator() ( CStudent &a, CStudent &b )
{

return a.num < b.num;
}
};

bool rankStudent(const CStudent &stu1, const CStudent &stu2)

{

return stu1.num > stu2.num;

}

int _tmain(int argc, _TCHAR* argv[])

{

vector<CStudent> vec;

for (int i = 0; i < 10; i++)

{

CStudent stu;

stu.num = rand();

vec.push_back(stu);

}

//sort(vec.begin(), vec.end());

sort(vec.begin(), vec.end(), rankStudent);

for (int i = 0; i < 10; i++)

{

cout<<vec[i].num<<"\t";

}

priority_queue<CStudent/*,vector<CStudent>,cmp*/> tmpQueue;
for (int i = 0; i < 10; i++)
{
CStudent stu;
stu.num = rand();
tmpQueue.push(stu);
}

while(!tmpQueue.empty())
{
CStudent &stu = tmpQueue.top();
cout<<stu.num<<"\t";
tmpQueue.pop();
}

getchar();

return 0;

}

unsigned long long hashCode(std::string str)
{
unsigned long long ulRet = 0;

for (unsigned int i = 0; i < str.size(); i++)
{
ulRet = 31 * ulRet + str[i];
}

return ulRet;
}