add lifetime exercise

data/1.rust初阶/1.预备知识/1.rust简介/helloworld.md

@@ -18,8 +18,8 @@ fn main() {
 
 ```rust
 fn main() {
-    let str = "Hello,World!";
-    println!("{}", str);
+    let str1 = "Hello,World!";
+    println!("{}", str1);
 }
 ```
 

data/2.rust中阶/2.生命周期/config.json

 {
   "node_id": "rust-d38898d251df42d49f5f367f077ede55",
-  "keywords": []
+  "keywords": [],
+  "children":[],
+  "export": [
+    "lifetime.json"
+  ]
 }
\ No newline at end of file

data/2.rust中阶/2.生命周期/lifetime.json

+{
+    "type": "code_options",
+    "author": "huanhuilong",
+    "source": "lifetime.md",
+    "notebook_enable": false
+}
\ No newline at end of file

data/2.rust中阶/2.生命周期/lifetime.md

+# Rust 函数的生命周期
+
+选出以下Rust代码中，生命周期错误的选项
+
+## 答案
+
+```rust
+// compile error!
+// where am I come from?
+fn process_objs(x:&Obejct, y:&Object):&Object{ 
+  if(x.is_ok()){
+    &x
+  }else{
+    &y
+  }
+}
+```
+
+## 选项
+
+### 如果这个借用本来就是从外部传入的，那当然可以返回，函数结束后这个对象还是有效的
+
+```rust
+// I am borrowed from caller
+// return borrow to the caller is safe
+fn process_obj(obj:&Object):&Object{
+  &obj
+}
+```
+
+### 显式添加生命周期标记
+
+```rust
+// I am come from 'a lifetime, NOT 'b
+fn process_objs<'a,'b>(x: &'a Obejct, y:&'b Object):&'a Object{ 
+  &x
+}
+```
+
+### 显式添加生命周期标记，解决歧义
+
+```rust
+// I am come from 'a lifetime, x,y,and result are all 'a lifetime
+fn process_objs<'a>(x: &'a Obejct, y:&'a Object):&'a Object{ 
+  if(x.is_ok()){
+    &x
+  }else{
+    &y
+  }
+}
+```

data/tree.json

@@ -4,7 +4,7 @@
     "keywords": [],
     "children": [
       {
-        "Rust初阶": {
+        "rust初阶": {
           "node_id": "rust-e2292238ccbf403d85fb20dd7b4c85ad",
           "keywords": [],
           "children": [
@@ -14,7 +14,7 @@
                 "keywords": [],
                 "children": [
                   {
-                    "Rust简介": {
+                    "rust简介": {
                       "node_id": "rust-7c394f164d8f44519521f03db08a1321",
                       "keywords": [],
                       "children": [
@@ -68,7 +68,7 @@
                     }
                   },
                   {
-                    "Rust安装": {
+                    "rust安装": {
                       "node_id": "rust-502b3cef4dbc41fdad069522470f3662",
                       "keywords": [],
                       "children": [
@@ -96,7 +96,7 @@
                     }
                   },
                   {
-                    "认识Rust工具链": {
+                    "认识rust工具链": {
                       "node_id": "rust-0d9e5f9449b94aa692a363f21a66c8af",
                       "keywords": [],
                       "children": []
@@ -120,7 +120,7 @@
               }
             },
             {
-              "Rust基本概念": {
+              "rust基本概念": {
                 "node_id": "rust-2cea732119294abab6f2887a364b242a",
                 "keywords": [],
                 "children": [
@@ -272,7 +272,7 @@
         }
       },
       {
-        "Rust中阶": {
+        "rust中阶": {
           "node_id": "rust-7377966439734497b91f3d775f9b0e0d",
           "keywords": [],
           "children": [
@@ -387,7 +387,7 @@
         }
       },
       {
-        "Rust高阶": {
+        "rust高阶": {
           "node_id": "rust-981f4f37a8e547abb135f54592ac52a5",
           "keywords": [],
           "children": [
@@ -496,14 +496,14 @@
                     }
                   },
                   {
-                    "用Rust实现X算法": {
+                    "用rust实现X算法": {
                       "node_id": "rust-d935276e360d41deb87caa06272c1ade",
                       "keywords": [],
                       "children": []
                     }
                   },
                   {
-                    "用Rust解X题": {
+                    "用rust解X题": {
                       "node_id": "rust-f8981b363064411c86d033f391ec133c",
                       "keywords": [],
                       "children": []