堆排序

class Finder {
public:
    int findKth(vector<int> a, int n, int K) {
        // write code here

        //假设int myints[] = {10,20,30,5,15};
        //建立最大堆，会使得a[n-1]放的是最大值30
        make_heap(a.begin(),a.end());

        //在已经建立好的堆上面，进行堆排序，使得5,10,15,20,30
        sort_heap(a.begin(),a.end());

        return a[n-K];
    }
};