Watch 10 video solutions for Number of Music Playlists, a hard level problem involving Math, Dynamic Programming, Combinatorics. This walkthrough by NeetCodeIO has 14,314 views views. Want to try solving it yourself? Practice on FleetCode or read the detailed text solution.
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:
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