leetcode 347 (堆排序)

void topdown(map<int,int> &m,vector<int> &heap,int size,int r)
    {
        int tmp=heap[r];
        int i;
        for(i=r;i*2+1<size;)
        {
            int j=i*2+1;
            if(j<size-1&&m[heap[j]]<m[heap[j+1]])
                j++;
            if(m[tmp]<m[heap[j]])
            {
                heap[i]=heap[j];
                i=j;
            }
            else
            {
                break;
            }
        }
        heap[i]=tmp;
    }
    
    vector<int> topKFrequent(vector<int>& nums, int k) {
        map<int,int> m;
        int len=nums.size();
        vector<int> heap;
        for(int i=0;i<len;i++)
        {
            m[nums[i]]++;
            if(m[nums[i]]==1)
                heap.push_back(nums[i]);
        }
        int s=heap.size();
        for(int i=s/2-1;i>=0;i--)
        {
            topdown(m,heap,s,i);
        }
        for(int i=0;i<k;i++)
        {
            int tmp=heap[0];
            heap[0]=heap[s-1-i];
            heap[s-1-i]=tmp;
            topdown(m,heap,s-i-1,0);
        }
        vector<int> res(k);
        for(int i=0;i<k;i++)
            res[i]=heap[s-i-1];
        return res;
    }