统计词频最高的前k个数
importjava.util.Comparator;importjava.util.HashMap;importjava.util.PriorityQueue;publicclassProblem_0347_TopKFrequentElements{publicstaticclassNode{publicintnum;publicintcount;publicNode(intk){num=k;count=1;}}publicstaticclassCountComparatorimplementsComparator<Node>{@Overridepublicintcompare(Nodeo1,Nodeo2){returno1.count-o2.count;}}publicstaticint[]topKFrequent(int[]nums,intk){intN=nums.length;HashMap<Integer,Node>map=newHashMap<>();for(intnum:nums){if(!map.containsKey(num)){map.put(num,newNode(num));}else{map.get(num).count++;}}PriorityQueue<Node>pq=newPriorityQueue<>(newCountComparator());for(Nodenode:map.values()){if(pq.size()<k||(pq.size()==k&&pq.peek().count<node.count)){pq.add(node);}if(pq.size()>k){pq.poll();}}int[]ans=newint[k];inti=0;while(!pq.isEmpty()){ans[i++]=pq.poll().num;}returnans;}publicstaticvoidmain(String[]args){int[]nums={1,1,1,1,1,1,1,1,2,2,3,3,3,4,4,4,4,5,5,5,5,5};int[]ans=topKFrequent(nums,2);for(inti=0;i<ans.length;i++){System.out.println(ans[i]);}}}
