[leetcode][920] Number of Music Playlists : https://leetcode.com/problems/number-of-music-playlists/

Number of Music Playlists.cc

class Solution {
public:
    int numMusicPlaylists(int N, int L, int K) {
        //dp[N][L] = 노래 N개로 L만큼 들는 경우의 수
        vector<vector<int>> dp(N+1, vector<int>(L+1,0));
        int mod = 1e9 + 7;
        
        dp[0][0] = 1;
        for(int i= 1;i<=N;i++){
            for(int j=1;j<=L;j++){
                dp[i][j] = ((long long int)dp[i-1][j-1] * (N - (i-1)) + (long long int)dp[i][j-1] * max(0, i-K)) % mod;
            }
        }
        return dp[N][L];
    }
};