Sort Features by Popularity

给一个features数组, 和一个responses数组, 求responses出现每个feature的次数, 从大到小.

class Solution {
    Map<String, Integer> map = new HashMap<>();
    public String[] sortFeatures(String[] features, String[] responses) {
        for(String f : features) {
            map.put(f, 0);
        }
        for(String r : responses){
            String[] strs = r.split(" ");
            Set<String> set = new HashSet<>();
            for(String s : strs) {
                if(map.containsKey(s) && !set.contains(s)){
                    set.add(s);
                    map.put(s, map.get(s) + 1);
                }
            }
        }
        Arrays.sort(features, (a,b) ->(appearances(b) - appearances(a)));
        return features;
    }
    private int appearances(String s) {
        return map.get(s);
    }
}