Package 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.<p>Hard</p> <p>Your music player contains <code>n</code> different songs. You want to listen to <code>goal</code> songs (not necessarily different) during your trip. To avoid boredom, you will create a playlist so that:</p> <ul> <li>Every song is played <strong>at least once</strong>.</li> <li>A song can only be played again only if <code>k</code> other songs have been played.</li> </ul> <p>Given <code>n</code>, <code>goal</code>, and <code>k</code>, return <em>the number of possible playlists that you can create</em>. Since the answer can be very large, return it <strong>modulo</strong> <code>10⁹ + 7</code>.</p> <p><strong>Example 1:</strong></p> <p><strong>Input:</strong> n = 3, goal = 3, k = 1</p> <p><strong>Output:</strong> 6</p> <p><strong>Explanation:</strong> There are 6 possible playlists: [1, 2, 3], [1, 3, 2], [2, 1, 3], [2, 3, 1], [3, 1, 2], and [3, 2, 1].</p> <p><strong>Example 2:</strong></p> <p><strong>Input:</strong> n = 2, goal = 3, k = 0</p> <p><strong>Output:</strong> 6</p> <p><strong>Explanation:</strong> There are 6 possible playlists: [1, 1, 2], [1, 2, 1], [2, 1, 1], [2, 2, 1], [2, 1, 2], and [1, 2, 2].</p> <p><strong>Example 3:</strong></p> <p><strong>Input:</strong> n = 2, goal = 3, k = 1</p> <p><strong>Output:</strong> 2</p> <p><strong>Explanation:</strong> There are 2 possible playlists: [1, 2, 1] and [2, 1, 2].</p> <p><strong>Constraints:</strong></p> <ul> <li><code>0 <= k < n <= goal <= 100</code></li> </ul>

Constructor Summary

Constructors

Constructor	Description
Solution()

Method Summary

Modifier and Type	Method	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 Details

Solution

public Solution()

Method Details

numMusicPlaylists

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