题解 | #字符串出现次数的TopK问题#

import java.util.*;


public class Solution {
    /**
     * return topK string
     * @param strings string字符串一维数组 strings
     * @param k int整型 the k
     * @return string字符串二维数组
     */
    public String[][] topKstrings (String[] strings, int k) {
        // write code here
        if(k==0){
            return new String[][]{};
        }
        String[][] res =new String[k][2];
        TreeMap<String,Integer> map=new TreeMap<>();
        //统计各个字符串出现的次数
        for(int i=0;i<strings.length;++i){
            String s=strings[i];
            if(!map.containsKey(s)){
                map.put(s,1);
            }else{
                map.put(s,map.get(s)+1);
            }
        }
        ArrayList<Map.Entry<String,Integer>> list=new ArrayList<>(map.entrySet());
        Collections.sort(list,
                    (o1, o2) ->
                    (o1.getValue().compareTo(o2.getValue()) ==
                     0 ? o1.getKey().compareTo(o2.getKey()) :
                     o2.getValue().compareTo(o1.getValue()))
                   );
        for (int i = 0; i < k; i++) {
            res[i][0] = list.get(i).getKey();
            res[i][1] = String.valueOf(list.get(i).getValue());
        }
        return res;
    }
}