vector pair sort

bool strict_weak_ordering(const std::pair<int, std::string> a, const std::pair<int,   std::string>   b)
{
return a.first < b.first;
}

int main()
{
　　using namespace std;

　　vector<pair<int, string> > vec;

vec.push_back(make_pair<int, string>(5, "hello"));
vec.push_back(make_pair<int, string>(4, "hell"));
vec.push_back(make_pair<int, string>(6, "hello,"));

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

vector<pair<int, string> >::iterator it = vec.begin(), end = vec.end();

for(; it != end; ++it)
　　cout<<it->second<<endl;
　　return 0;
}