Top K Frequent Elements
给一个数组, 返回前k个高频数字.
public class Solution {
public List<Integer> topKFrequent(int[] nums, int k) {
Map<Integer, Integer> map = new HashMap<>();
for(int i : nums){
if(map.containsKey(i))
map.put(i,map.get(i)+1);
else
map.put(i,0);
}
PriorityQueue<Map.Entry<Integer,Integer>> pq = new PriorityQueue<>((a, b) -> a.getValue()-b.getValue());
for(Map.Entry<Integer,Integer> e : map.entrySet()){
pq.add(e);
if(pq.size()>k)
pq.poll();
}
List<Integer> res = new ArrayList<Integer>();
while(!pq.isEmpty()){
res.add(pq.poll().getKey());
}
return res;
}
}