feat: add rust solution to lc problem: No.0920 (#1409)

Author: xzhseh

solution/0900-0999/0920.Number of Music Playlists/README.md

@@ -204,6 +204,40 @@ public:
 };
 ```
 
+### **Rust**
+
+```rust
+impl Solution {
+    #[allow(dead_code)]
+    pub fn num_music_playlists(n: i32, goal: i32, k: i32) -> i32 {
+        let mut dp: Vec<Vec<i64>> = vec![vec![0; n as usize + 1]; goal as usize + 1];
+
+        // Initialize the dp vector
+        dp[0][0] = 1;
+
+        // Begin the dp process
+        for i in 1..=goal as usize {
+            for j in 1..=n as usize {
+                // Choose the song that has not been chosen before
+                // We have n - (j - 1) songs to choose
+                dp[i][j] += dp[i - 1][j - 1] * ((n - (j as i32 - 1))) as i64;
+                
+                // Choose the song that has been chosen before
+                // We have j - k songs to choose if j > k
+                if j as i32 > k {
+                    dp[i][j] += dp[i - 1][j] * (j as i32 - k) as i64;
+                }
+
+                // Update dp[i][j]
+                dp[i][j] %= (1e9 as i32 + 7) as i64;
+            }
+        }
+
+        dp[goal as usize][n as usize] as i32
+    }
+}
+```
+
 ### **Go**
 
 ```go

solution/0900-0999/0920.Number of Music Playlists/README_EN.md

@@ -194,6 +194,40 @@ public:
 };
 ```
 
+### **Rust**
+
+```rust
+impl Solution {
+    #[allow(dead_code)]
+    pub fn num_music_playlists(n: i32, goal: i32, k: i32) -> i32 {
+        let mut dp: Vec<Vec<i64>> = vec![vec![0; n as usize + 1]; goal as usize + 1];
+
+        // Initialize the dp vector
+        dp[0][0] = 1;
+
+        // Begin the dp process
+        for i in 1..=goal as usize {
+            for j in 1..=n as usize {
+                // Choose the song that has not been chosen before
+                // We have n - (j - 1) songs to choose
+                dp[i][j] += dp[i - 1][j - 1] * ((n - (j as i32 - 1))) as i64;
+                
+                // Choose the song that has been chosen before
+                // We have j - k songs to choose if j > k
+                if j as i32 > k {
+                    dp[i][j] += dp[i - 1][j] * (j as i32 - k) as i64;
+                }
+
+                // Update dp[i][j]
+                dp[i][j] %= (1e9 as i32 + 7) as i64;
+            }
+        }
+
+        dp[goal as usize][n as usize] as i32
+    }
+}
+```
+
 ### **Go**
 
 ```go

solution/0900-0999/0920.Number of Music Playlists/Solution.rs

@@ -0,0 +1,29 @@
+impl Solution {
+    #[allow(dead_code)]
+    pub fn num_music_playlists(n: i32, goal: i32, k: i32) -> i32 {
+        let mut dp: Vec<Vec<i64>> = vec![vec![0; n as usize + 1]; goal as usize + 1];
+
+        // Initialize the dp vector
+        dp[0][0] = 1;
+
+        // Begin the dp process
+        for i in 1..=goal as usize {
+            for j in 1..=n as usize {
+                // Choose the song that has not been chosen before
+                // We have n - (j - 1) songs to choose
+                dp[i][j] += dp[i - 1][j - 1] * ((n - (j as i32 - 1))) as i64;
+                
+                // Choose the song that has been chosen before
+                // We have j - k songs to choose if j > k
+                if j as i32 > k {
+                    dp[i][j] += dp[i - 1][j] * (j as i32 - k) as i64;
+                }
+
+                // Update dp[i][j]
+                dp[i][j] %= (1e9 as i32 + 7) as i64;
+            }
+        }
+
+        dp[goal as usize][n as usize] as i32
+    }
+}