feat: add rust solution to lc problem: No.0114 (#1280)

Author: xzhseh

solution/0100-0199/0114.Flatten Binary Tree to Linked List/README.md

@@ -166,6 +166,60 @@ public:
 };
 ```
 
+### **Rust**
+
+```rust
+// Definition for a binary tree node.
+// #[derive(Debug, PartialEq, Eq)]
+// pub struct TreeNode {
+//   pub val: i32,
+//   pub left: Option<Rc<RefCell<TreeNode>>>,
+//   pub right: Option<Rc<RefCell<TreeNode>>>,
+// }
+// 
+// impl TreeNode {
+//   #[inline]
+//   pub fn new(val: i32) -> Self {
+//     TreeNode {
+//       val,
+//       left: None,
+//       right: None
+//     }
+//   }
+// }
+use std::rc::Rc;
+use std::cell::RefCell;
+impl Solution {
+    #[allow(dead_code)]
+    pub fn flatten(root: &mut Option<Rc<RefCell<TreeNode>>>) {
+        if root.is_none() {
+            return;
+        }
+        let mut v: Vec<Option<Rc<RefCell<TreeNode>>>> = Vec::new();
+        // Initialize the vector
+        Self::pre_order_traverse(&mut v, root);
+        // Traverse the vector
+        let n = v.len();
+        for i in 0..n - 1 {
+            v[i].as_ref().unwrap().borrow_mut().left = None;
+            v[i].as_ref().unwrap().borrow_mut().right = v[i + 1].clone();
+        }
+    }
+
+    #[allow(dead_code)]
+    fn pre_order_traverse(v: &mut Vec<Option<Rc<RefCell<TreeNode>>>>, root: &Option<Rc<RefCell<TreeNode>>>) {
+        if root.is_none() {
+            return;
+        }
+        v.push(root.clone());
+        let left = root.as_ref().unwrap().borrow().left.clone();
+        let right = root.as_ref().unwrap().borrow().right.clone();
+        Self::pre_order_traverse(v, &left);
+        Self::pre_order_traverse(v, &right);
+    }
+}
+```
+
 ### **Go**
 
 ```go

solution/0100-0199/0114.Flatten Binary Tree to Linked List/README_EN.md

@@ -142,6 +142,60 @@ public:
 };
 ```
 
+### **Rust**
+
+```rust
+// Definition for a binary tree node.
+// #[derive(Debug, PartialEq, Eq)]
+// pub struct TreeNode {
+//   pub val: i32,
+//   pub left: Option<Rc<RefCell<TreeNode>>>,
+//   pub right: Option<Rc<RefCell<TreeNode>>>,
+// }
+// 
+// impl TreeNode {
+//   #[inline]
+//   pub fn new(val: i32) -> Self {
+//     TreeNode {
+//       val,
+//       left: None,
+//       right: None
+//     }
+//   }
+// }
+use std::rc::Rc;
+use std::cell::RefCell;
+impl Solution {
+    #[allow(dead_code)]
+    pub fn flatten(root: &mut Option<Rc<RefCell<TreeNode>>>) {
+        if root.is_none() {
+            return;
+        }
+        let mut v: Vec<Option<Rc<RefCell<TreeNode>>>> = Vec::new();
+        // Initialize the vector
+        Self::pre_order_traverse(&mut v, root);
+        // Traverse the vector
+        let n = v.len();
+        for i in 0..n - 1 {
+            v[i].as_ref().unwrap().borrow_mut().left = None;
+            v[i].as_ref().unwrap().borrow_mut().right = v[i + 1].clone();
+        }
+    }
+
+    #[allow(dead_code)]
+    fn pre_order_traverse(v: &mut Vec<Option<Rc<RefCell<TreeNode>>>>, root: &Option<Rc<RefCell<TreeNode>>>) {
+        if root.is_none() {
+            return;
+        }
+        v.push(root.clone());
+        let left = root.as_ref().unwrap().borrow().left.clone();
+        let right = root.as_ref().unwrap().borrow().right.clone();
+        Self::pre_order_traverse(v, &left);
+        Self::pre_order_traverse(v, &right);
+    }
+}
+```
+
 ### **Go**
 
 ```go

solution/0100-0199/0114.Flatten Binary Tree to Linked List/Solution.rs

@@ -0,0 +1,49 @@
+// Definition for a binary tree node.
+// #[derive(Debug, PartialEq, Eq)]
+// pub struct TreeNode {
+//   pub val: i32,
+//   pub left: Option<Rc<RefCell<TreeNode>>>,
+//   pub right: Option<Rc<RefCell<TreeNode>>>,
+// }
+// 
+// impl TreeNode {
+//   #[inline]
+//   pub fn new(val: i32) -> Self {
+//     TreeNode {
+//       val,
+//       left: None,
+//       right: None
+//     }
+//   }
+// }
+use std::rc::Rc;
+use std::cell::RefCell;
+impl Solution {
+    #[allow(dead_code)]
+    pub fn flatten(root: &mut Option<Rc<RefCell<TreeNode>>>) {
+        if root.is_none() {
+            return;
+        }
+        let mut v: Vec<Option<Rc<RefCell<TreeNode>>>> = Vec::new();
+        // Initialize the vector
+        Self::pre_order_traverse(&mut v, root);
+        // Traverse the vector
+        let n = v.len();
+        for i in 0..n - 1 {
+            v[i].as_ref().unwrap().borrow_mut().left = None;
+            v[i].as_ref().unwrap().borrow_mut().right = v[i + 1].clone();
+        }
+    }
+
+    #[allow(dead_code)]
+    fn pre_order_traverse(v: &mut Vec<Option<Rc<RefCell<TreeNode>>>>, root: &Option<Rc<RefCell<TreeNode>>>) {
+        if root.is_none() {
+            return;
+        }
+        v.push(root.clone());
+        let left = root.as_ref().unwrap().borrow().left.clone();
+        let right = root.as_ref().unwrap().borrow().right.clone();
+        Self::pre_order_traverse(v, &left);
+        Self::pre_order_traverse(v, &right);
+    }
+}