Number of Music Playlists LeetCode solution in JavaScript

1
/**
2
 * @param {number} n
3
 * @param {number} goal
4
 * @param {number} k
5
 * @return {number}
6
 */
7
var numMusicPlaylists = function (n, goal, k) {
8
  const MOD = 1e9 + 7;
9
  let dp = Array.from({ length: 2 }, () => new Array(n + 1).fill(0));
10
  dp[0][0] = 1;
11

12
  for (let i = 1; i <= goal; i++) {
13
    dp[i % 2][0] = 0;
14
    for (let j = 1; j <= Math.min(i, n); j++) {
15
      dp[i % 2][j] = (dp[(i - 1) % 2][j - 1] * (n - (j - 1))) % MOD;
16
      if (j > k)
17
        dp[i % 2][j] = (dp[i % 2][j] + dp[(i - 1) % 2][j] * (j - k)) % MOD;
18
    }
19
  }
20

21
  return dp[goal % 2][n];
22
};