0920-number-of-music-playlists.adoc

920. Number of Music Playlists

{leetcode}/problems/number-of-music-playlists/[LeetCode - Number of Music Playlists^]

Your music player contains N different songs and she wants to listen to L* *(not necessarily different) songs during your trip. You 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

Return the number of possible playlists. As the answer can be very large, return it modulo 10^9 + 7.

Example 1:

Input: N = 3, L = 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], [3, 2, 1].

Example 2:

Input: N = 2, L = 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], [1, 2, 2]

Example 3:

Input: N = 2, L = 3, K = 1
Output: 2
Explanation: There are 2 possible playlists. [1, 2, 1], [2, 1, 2]

Note:

• 0 ⇐ K < N ⇐ L ⇐ 100

link:{sourcedir}/_0920_NumberOfMusicPlaylists.java[role=include]