feat: add rust solution to lc problem: No.0258

No.0258.Add Digits

Author: YangFong

solution/0200-0299/0258.Add Digits/README.md

@@ -55,7 +55,6 @@ class Solution:
 
 ```java
 class Solution {
-
     public int addDigits(int num) {
         return (num - 1) % 9 + 1;
     }
@@ -85,6 +84,32 @@ func addDigits(num int) int {
 }
 ```
 
+### **Rust**
+
+```rust
+impl Solution {
+    pub fn add_digits(num: i32) -> i32 {
+        if num < 10 {
+            return num;
+        }
+        Self::add_digits(
+            num.to_string()
+                .chars()
+                .map(|c| c.to_string().parse::<i32>().unwrap())
+                .sum::<i32>(),
+        )
+    }
+}
+```
+
+```rust
+impl Solution {
+    pub fn add_digits(mut num: i32) -> i32 {
+        (num - 1) % 9 + 1
+    }
+}
+```
+
 ### **...**
 
 ```

solution/0200-0299/0258.Add Digits/README_EN.md

@@ -51,7 +51,6 @@ class Solution:
 
 ```java
 class Solution {
-
     public int addDigits(int num) {
         return (num - 1) % 9 + 1;
     }
@@ -81,6 +80,32 @@ func addDigits(num int) int {
 }
 ```
 
+### **Rust**
+
+```rust
+impl Solution {
+    pub fn add_digits(num: i32) -> i32 {
+        if num < 10 {
+            return num;
+        }
+        Self::add_digits(
+            num.to_string()
+                .chars()
+                .map(|c| c.to_string().parse::<i32>().unwrap())
+                .sum::<i32>(),
+        )
+    }
+}
+```
+
+```rust
+impl Solution {
+    pub fn add_digits(mut num: i32) -> i32 {
+        (num - 1) % 9 + 1
+    }
+}
+```
+
 ### **...**
 
 ```

solution/0200-0299/0258.Add Digits/Solution.rs

@@ -0,0 +1,5 @@
+impl Solution {
+    pub fn add_digits(mut num: i32) -> i32 {
+        (num - 1) % 9 + 1
+    }
+}