g0901_1000.s0920_number_of_music_playlists

Class Solution

java.lang.Object

g0901_1000.s0920_number_of_music_playlists.Solution

public class Solution
extends Object

920 - Number of Music Playlists.

Hard

Your music player contains n different songs. You want to listen to goal songs (not necessarily different) during your trip. To avoid boredom, you will create a playlist so that:

• Every song is played at least once.
• A song can only be played again only if k other songs have been played.

Given n, goal, and k, return the number of possible playlists that you can create. Since the answer can be very large, return it modulo 109 + 7.

Example 1:

Input: n = 3, goal = 3, k = 1

Output: 6

Explanation: There are 6 possible playlists: [1, 2, 3], [1, 3, 2], [2, 1, 3], [2, 3, 1], [3, 1, 2], and [3, 2, 1].

Example 2:

Input: n = 2, goal = 3, k = 0

Output: 6

Explanation: There are 6 possible playlists: [1, 1, 2], [1, 2, 1], [2, 1, 1], [2, 2, 1], [2, 1, 2], and [1, 2, 2].

Example 3:

Input: n = 2, goal = 3, k = 1

Output: 2

Explanation: There are 2 possible playlists: [1, 2, 1] and [2, 1, 2].

Constraints:

• 0 <= k < n <= goal <= 100

Constructor Summary

Constructors

Constructor and Description
Solution()

Method Summary

Modifier and Type	Method and Description
int	numMusicPlaylists(int n, int l, int k)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

Solution

public Solution()

Method Detail

numMusicPlaylists

public int numMusicPlaylists(int n,
                             int l,
                             int k)