feat: add rust solution to lc problem: No.0202

No.0202.Happy Number

Author: YangFong

solution/0200-0299/0202.Happy Number/README.md

@@ -51,6 +51,12 @@
 
 <!-- 这里可写通用的实现逻辑 -->
 
+简单模拟，有可能进入死循环导致无法停止，有几种方式解决：
+
+- 哈希表：转换过程不会重复出现同一个数字。
+- 限制转换次数：在一定次数转换后还未成功变为 1，那么就断言此数不是快乐数。
+- 快慢指针：与判断链表是否存在环原理一致。
+
 <!-- tabs:start -->
 
 ### **Python3**
@@ -101,6 +107,31 @@ class Solution {
 }
 ```
 
+### **Rust**
+
+```rust
+impl Solution {
+    fn get_next(mut n: i32) -> i32 {
+        let mut res = 0;
+        while n != 0 {
+            res += (n % 10).pow(2);
+            n /= 10;
+        }
+        res
+    }
+
+    pub fn is_happy(n: i32) -> bool {
+        let mut slow = n;
+        let mut fast = Self::get_next(n);
+        while slow != fast {
+            slow = Self::get_next(slow);
+            fast = Self::get_next(Self::get_next(fast));
+        }
+        slow == 1
+    }
+}
+```
+
 ### **...**
 
 ```

solution/0200-0299/0202.Happy Number/README_EN.md

@@ -91,6 +91,31 @@ class Solution {
 }
 ```
 
+### **Rust**
+
+```rust
+impl Solution {
+    fn get_next(mut n: i32) -> i32 {
+        let mut res = 0;
+        while n != 0 {
+            res += (n % 10).pow(2);
+            n /= 10;
+        }
+        res
+    }
+
+    pub fn is_happy(n: i32) -> bool {
+        let mut slow = n;
+        let mut fast = Self::get_next(n);
+        while slow != fast {
+            slow = Self::get_next(slow);
+            fast = Self::get_next(Self::get_next(fast));
+        }
+        slow == 1
+    }
+}
+```
+
 ### **...**
 
 ```

solution/0200-0299/0202.Happy Number/Solution.rs

@@ -0,0 +1,20 @@
+impl Solution {
+    fn get_next(mut n: i32) -> i32 {
+        let mut res = 0;
+        while n != 0 {
+            res += (n % 10).pow(2);
+            n /= 10;
+        }
+        res
+    }
+
+    pub fn is_happy(n: i32) -> bool {
+        let mut slow = n;
+        let mut fast = Self::get_next(n);
+        while slow != fast {
+            slow = Self::get_next(slow);
+            fast = Self::get_next(Self::get_next(fast));
+        }
+        slow == 1
+    }
+}