refactor(part5): 替换原有枚举示例为Status枚举

更新了part5的main.rs代码，移除了Direction和IpAddr枚举，改用Status枚举作为演示示例；同时补充了枚举相关练习题的参考解答代码。

part5/enum练习题.md

@@ -89,6 +89,8 @@ fn main() {
 }
 ```
 
+> 可以通过
+
 ### 题目 1-5
 
 ```rust
@@ -99,6 +101,8 @@ fn main() {
 }
 ```
 
+> 不能，Option枚举类型不能直接用+，需要实现add方法
+
 ### 题目 1-6
 
 ```rust
@@ -122,6 +126,8 @@ fn main() {
 }
 ```
 
+> 不能，match需要匹配所有可能出现的类型
+
 ### 题目 1-7
 
 ```rust
@@ -139,6 +145,8 @@ fn main() {
 }
 ```
 
+> 可以
+
 ### 题目 1-8
 
 ```rust
@@ -161,6 +169,8 @@ fn main() {
 }
 ```
 
+> 可以
+
 ***
 
 ## 二、填空题：补充代码
@@ -188,6 +198,23 @@ fn main() {
 }
 ```
 
+```rust
+enum TrafficLight {
+    Red,
+    Yellow,
+    Green,
+}
+
+fn main() {
+    let light = TrafficLight::Red;
+    match light {
+        TrafficLight::Red => println!("停止"),
+        TrafficLight::Yellow => println!("减速"),
+        TrafficLight::Green => println!("通行"),
+    }
+}
+```
+
 ### 题目 2-2：带数据的枚举
 
 ```rust
@@ -209,6 +236,21 @@ fn main() {
 }
 ```
 
+```rust
+enum WebEvent {
+    PageLoad,
+    KeyPress(char),
+    Click { x: i32, y: i32 },
+}
+
+fn main() {
+    let load = WebEvent::PageLoad;
+    let key = WebEvent::KeyPress('a');
+    let click = WebEvent::Click { x: 100, y: 200 };
+    println!("ok");
+}
+```
+
 ### 题目 2-3：Option 的使用
 
 ```rust
@@ -230,6 +272,23 @@ fn main() {
 }
 ```
 
+```rust
+fn main() {
+    let v1 = Some(10);
+    let v2: Option<i32> = None;
+
+    let val1 = match v1 {
+        Some(n) => n,
+        None => 0,
+    };
+    let val2 = match v2 {
+        Some(n) => n,
+        None => 0,
+    };
+    println!("val1: {}, val2: {}", val1, val2);
+}
+```
+
 ### 题目 2-4：Result 的使用
 
 ```rust
@@ -261,6 +320,31 @@ fn main() {
 }
 ```
 
+```rust
+fn divide(a: i32, b: i32) -> Result<i32, String> {
+    if b == 0 {
+        Err(String::from("除数不能为零"))
+    } else {
+        Ok(a / b)
+    }
+}
+
+fn main() {
+    let result1 = divide(10, 2);
+    let result2 = divide(10, 0);
+
+    match result1 {
+        Ok(val) => println!("结果: {}", val),
+        Err(e) => println!("错误: {}", e),
+    }
+
+    match result2 {
+        Ok(val) => println!("结果: {}", val),
+        Err(e) => println!("错误: {}", e),
+    }
+}
+```
+
 ### 题目 2-5：枚举上的方法
 
 ```rust
@@ -290,6 +374,32 @@ fn main() {
 }
 ```
 
+```rust
+enum Message {
+    Quit,
+    Write(String),
+    Move { x: i32, y: i32 },
+}
+
+impl Message {
+    fn call(&self) {
+        match self {
+            Message::Quit => println!("退出"),
+            Message::Write(text) => println!("写入: {}", text),
+            Message::Move { x, y } => println!("移动到 ({}, {})", x, y),
+        }
+    }
+}
+
+fn main() {
+    let m = Message::Write(String::from("你好世界"));
+    m.call();
+
+    let n = Message::Move { x: 10, y: 20 };
+    n.call();
+}
+```
+
 ### 题目 2-6：if let 语法
 
 ```rust
@@ -310,6 +420,16 @@ fn main() {
 }
 ```
 
+```rust
+fn main() {
+    let config_max = Some(3u8);
+
+    if let Some(max) = config_max {
+        println!("最大值为: {}", max);
+    }
+}
+```
+
 ### 题目 2-7：嵌套 Option 处理
 
 ```rust
@@ -326,6 +446,18 @@ fn main() {
 }
 ```
 
+```rust
+fn main() {
+    let opt: Option<Option<i32>> = Some(Some(42));
+
+    match opt {
+        Some(Some(inner)) => println!("值是: {}", inner),
+        Some(None) => println!("内层是 None"),
+        None => println!("外层是 None"),
+    }
+}
+```
+
 ### 题目 2-8：match 的多种模式
 
 ```rust
@@ -342,6 +474,18 @@ fn main() {
 }
 ```
 
+```rust
+fn main() {
+    let x = 3;
+
+    match x {
+        1 | 2 => println!("是 1 或 2"),
+        3..=8 => println!("在 3 到 8 之间"),
+        _ => println!("其他值"),
+    }
+}
+```
+
 ***
 
 ## 三、找出并修复错误
@@ -362,6 +506,19 @@ fn main() {
 }
 ```
 
+```rust
+#[derive(Debug)]
+enum Status {
+    Active,
+    Inactive,
+}
+
+fn main() {
+    let s = Status::Active;
+    println!("{:?}", s);
+}
+```
+
 ### 题目 3-2
 
 ```rust

part5/src/main.rs

@@ -1,19 +1,10 @@
 #[derive(Debug)]
-enum Direction {
-    North,
-    South,
-    East,
-    West,
-}
-
-enum IpAddr {
-    V4(String),
-    V6(String),
+enum Status {
+    Active,
+    Inactive,
 }
 
 fn main() {
-    let direction = Direction::North;
-    println!(" direction: {:?}", direction);
-    let home = IpAddr::V4(String::from("127.0.0.1"));
-    // println!(" home: {:?}", home);
+    let s = Status::Active;
+    println!("{:?}", s);
 }