Given a map Map<String, List<String>> userSongs with user names as keys and a list of all the songs that the user has listened to as values.

Also given a map Map<String, List<String>> songGenres, with song genre as keys and a list of all the songs within that genre as values. The song can only belong to only one genre.

The task is to return a map Map<String, List<String>>, where the key is a user name and the value is a list of the user's favorite genre(s). Favorite genre is the most listened to genre. A user can have more than one favorite genre if he/she has listened to the same number of songs per each of the genres.

Example 1:

Input: userSongs = {

"David": ["song1", "song2", "song3", "song4", "song8"],

"Emma": ["song5", "song6", "song7"]

},

songGenres = {

"Rock": ["song1", "song3"],

"Dubstep": ["song7"],

"Techno": ["song2", "song4"],

"Pop": ["song5", "song6"],

"Jazz": ["song8", "song9"]

}

Output: {

"David": ["Rock", "Techno"],

"Emma": ["Pop"]

}

Explanation:

David has 2 Rock, 2 Techno and 1 Jazz song. So he has 2 favorite genres.

Emma has 2 Pop and 1 Dubstep song. Pop is Emma's favorite genre.

Example 2:

Input:

userSongs = {

"David": ["song1", "song2"],

"Emma": ["song3", "song4"]

},

songGenres = {}

Output: {

"David": [],

"Emma": []

}