C++基础之map按key排序

在项目当中有要用到map按key排序的需求，就在百度上搜了一下：

typedef pair<int,int> PAIR;

int cmp(const PAIR& x, const PAIR& y)
{
return x.second < y.second;
}

map<int,int> imgdis; //待排序对象，根据double值排序
imgdis[1] = 3;
imgdis[10] = 1;
imgdis[3] = 5;
imgdis[12] = 4;
imgdis[5] = 4;
vector<PAIR> vecpair;

for (map<int,int>::iterator curr = imgdis.begin(); curr != imgdis.end(); ++curr)
{
vecpair.push_back(make_pair(curr->first, curr->second));
}
sort(vecpair.begin(), vecpair.end(), cmp);

//输出排序后的键值对
for(int i = 0 ;i<vecpair.size();i++)
{
cout<<" "<<vecpair[i].first<<" "<<vecpair[i].second<<endl;
}

有更好的方法，欢迎推荐啊