feat: add rust solution to lc problem: No.1930 (#4854)

Author: yanglbme

solution/1900-1999/1930.Unique Length-3 Palindromic Subsequences/README.md

@@ -191,6 +191,33 @@ function countPalindromicSubsequence(s: string): number {
 }
 ```
 
+#### Rust
+
+```rust
+impl Solution {
+    pub fn count_palindromic_subsequence(s: String) -> i32 {
+        let s_bytes = s.as_bytes();
+        let mut ans = 0;
+        for c in b'a'..=b'z' {
+            if let (Some(l), Some(r)) = (
+                s_bytes.iter().position(|&ch| ch == c),
+                s_bytes.iter().rposition(|&ch| ch == c),
+            ) {
+                let mut mask = 0u32;
+                for i in (l + 1)..r {
+                    let j = (s_bytes[i] - b'a') as u32;
+                    if (mask >> j & 1) == 0 {
+                        mask |= 1 << j;
+                        ans += 1;
+                    }
+                }
+            }
+        }
+        ans
+    }
+}
+```
+
 #### JavaScript
 
 ```js

solution/1900-1999/1930.Unique Length-3 Palindromic Subsequences/README_EN.md

@@ -189,6 +189,33 @@ function countPalindromicSubsequence(s: string): number {
 }
 ```
 
+#### Rust
+
+```rust
+impl Solution {
+    pub fn count_palindromic_subsequence(s: String) -> i32 {
+        let s_bytes = s.as_bytes();
+        let mut ans = 0;
+        for c in b'a'..=b'z' {
+            if let (Some(l), Some(r)) = (
+                s_bytes.iter().position(|&ch| ch == c),
+                s_bytes.iter().rposition(|&ch| ch == c),
+            ) {
+                let mut mask = 0u32;
+                for i in (l + 1)..r {
+                    let j = (s_bytes[i] - b'a') as u32;
+                    if (mask >> j & 1) == 0 {
+                        mask |= 1 << j;
+                        ans += 1;
+                    }
+                }
+            }
+        }
+        ans
+    }
+}
+```
+
 #### JavaScript
 
 ```js

solution/1900-1999/1930.Unique Length-3 Palindromic Subsequences/Solution.rs

@@ -0,0 +1,22 @@
+impl Solution {
+    pub fn count_palindromic_subsequence(s: String) -> i32 {
+        let s_bytes = s.as_bytes();
+        let mut ans = 0;
+        for c in b'a'..=b'z' {
+            if let (Some(l), Some(r)) = (
+                s_bytes.iter().position(|&ch| ch == c),
+                s_bytes.iter().rposition(|&ch| ch == c),
+            ) {
+                let mut mask = 0u32;
+                for i in (l + 1)..r {
+                    let j = (s_bytes[i] - b'a') as u32;
+                    if (mask >> j & 1) == 0 {
+                        mask |= 1 << j;
+                        ans += 1;
+                    }
+                }
+            }
+        }
+        ans
+    }
+}