feat: add rust solution to lc problem: No.2549 (#1222)

Signed-off-by: xiaolatiao <1628652790@qq.com>

Author: dierbei

solution/2500-2599/2549.Count Distinct Numbers on Board/README.md

@@ -119,6 +119,20 @@ function distinctIntegers(n: number): number {
 }
 ```
 
+### **Rust**
+
+```rust
+impl Solution {
+    pub fn distinct_integers(n: i32) -> i32 {
+        if n == 1 {
+            return 1;
+        }
+
+        n - 1
+    }
+}
+```
+
 ### **...**
 
 ```

solution/2500-2599/2549.Count Distinct Numbers on Board/README_EN.md

@@ -101,6 +101,20 @@ function distinctIntegers(n: number): number {
 }
 ```
 
+### **Rust**
+
+```rust
+impl Solution {
+    pub fn distinct_integers(n: i32) -> i32 {
+        if n == 1 {
+            return 1;
+        }
+
+        n - 1
+    }
+}
+```
+
 ### **...**
 
 ```

solution/2500-2599/2549.Count Distinct Numbers on Board/Solution.rs

@@ -0,0 +1,9 @@
+impl Solution {
+    pub fn distinct_integers(n: i32) -> i32 {
+        if n == 1 {
+            return 1;
+        }
+
+        n - 1
+    }
+}