Merge pull request #1741 from Jack-Zhang-1314/patch-10

update 0102.二叉树的层序遍历.md about using vecdeque rust

problems/0102.二叉树的层序遍历.md

@@ -380,29 +380,32 @@ object Solution {
 Rust:
 
 ```rust
-pub fn level_order(root: Option<Rc<RefCell<TreeNode>>>) -> Vec<Vec<i32>> {
-    let mut ans = Vec::new();
-    let mut stack = Vec::new();
-    if root.is_none(){
-        return ans;
+use std::cell::RefCell;
+use std::rc::Rc;
+use std::collections::VecDeque;
+impl Solution {
+    pub fn level_order(root: Option<Rc<RefCell<TreeNode>>>) -> Vec<Vec<i32>> {
+        let mut res = vec![];
+        let mut queue = VecDeque::new();
+        if root.is_some() {
+            queue.push_back(root);
         }
-    stack.push(root.unwrap());
-    while stack.is_empty()!= true{
-        let num = stack.len();
-        let mut level = Vec::new();
-        for _i in 0..num{
-            let tmp = stack.remove(0);
-            level.push(tmp.borrow_mut().val);
-            if tmp.borrow_mut().left.is_some(){
-                stack.push(tmp.borrow_mut().left.take().unwrap());
+        while !queue.is_empty() {
+            let mut temp = vec![];
+            for _ in 0..queue.len() {
+                let node = queue.pop_front().unwrap().unwrap();
+                temp.push(node.borrow().val);
+                if node.borrow().left.is_some() {
+                    queue.push_back(node.borrow().left.clone());
                 }
-            if tmp.borrow_mut().right.is_some(){
-                stack.push(tmp.borrow_mut().right.take().unwrap());
+                if node.borrow().right.is_some() {
+                    queue.push_back(node.borrow().right.clone());
                 }
             }
-        ans.push(level);
+            res.push(temp);
+        }
+        res
     }
-    ans
 }
 ```
 
@@ -665,29 +668,32 @@ object Solution {
 Rust:
 
 ```rust
-pub fn level_order(root: Option<Rc<RefCell<TreeNode>>>) -> Vec<Vec<i32>> {
-    let mut ans = Vec::new();
-    let mut stack = Vec::new();
-    if root.is_none(){
-        return ans;
+use std::cell::RefCell;
+use std::collections::VecDeque;
+use std::rc::Rc;
+impl Solution {
+    pub fn level_order_bottom(root: Option<Rc<RefCell<TreeNode>>>) -> Vec<Vec<i32>> {
+        let mut res = vec![];
+        let mut queue = VecDeque::new();
+        if root.is_some() {
+            queue.push_back(root);
         }
-    stack.push(root.unwrap());
-    while stack.is_empty()!= true{
-        let num = stack.len();
-        let mut level = Vec::new();
-        for _i in 0..num{
-            let tmp = stack.remove(0);
-            level.push(tmp.borrow_mut().val);
-            if tmp.borrow_mut().left.is_some(){
-                stack.push(tmp.borrow_mut().left.take().unwrap());
+        while !queue.is_empty() {
+            let mut temp = vec![];
+            for _ in 0..queue.len() {
+                let node = queue.pop_front().unwrap().unwrap();
+                temp.push(node.borrow().val);
+                if node.borrow().left.is_some() {
+                    queue.push_back(node.borrow().left.clone());
                 }
-            if tmp.borrow_mut().right.is_some(){
-                stack.push(tmp.borrow_mut().right.take().unwrap());
+                if node.borrow().right.is_some() {
+                    queue.push_back(node.borrow().right.clone());
                 }
             }
-        ans.push(level);
+            res.push(temp);
+        }
+        res.into_iter().rev().collect()
     }
-    ans
 }
 ```
 
@@ -935,6 +941,39 @@ object Solution {
 }
 ```
 
+rust:
+
+```rust
+use std::cell::RefCell;
+use std::collections::VecDeque;
+use std::rc::Rc;
+impl Solution {
+    pub fn right_side_view(root: Option<Rc<RefCell<TreeNode>>>) -> Vec<i32> {
+        let mut res = vec![];
+        let mut queue = VecDeque::new();
+        if root.is_some() {
+            queue.push_back(root);
+        }
+        while !queue.is_empty() {
+            let len = queue.len();
+            for i in 0..len {
+                let node = queue.pop_front().unwrap().unwrap();
+                if i == len - 1 {
+                    res.push(node.borrow().val);
+                }
+                if node.borrow().left.is_some() {
+                    queue.push_back(node.borrow().left.clone());
+                }
+                if node.borrow().right.is_some() {
+                    queue.push_back(node.borrow().right.clone());
+                }
+            }
+        }
+        res
+    }
+}
+```
+
 # 637.二叉树的层平均值
 
 [力扣题目链接](https://leetcode.cn/problems/average-of-levels-in-binary-tree/)
@@ -1185,6 +1224,39 @@ object Solution {
 }
 ```
 
+rust:
+
+```rust
+use std::cell::RefCell;
+use std::collections::VecDeque;
+use std::rc::Rc;
+impl Solution {
+    pub fn average_of_levels(root: Option<Rc<RefCell<TreeNode>>>) -> Vec<f64> {
+        let mut res = vec![];
+        let mut queue = VecDeque::new();
+        if root.is_some() {
+            queue.push_back(root);
+        }
+        while !queue.is_empty() {
+            let len = queue.len();
+            let mut sum = 0;
+            for _ in 0..len {
+                let node = queue.pop_front().unwrap().unwrap();
+                sum += node.borrow().val;
+                if node.borrow().left.is_some() {
+                    queue.push_back(node.borrow().left.clone());
+                }
+                if node.borrow().right.is_some() {
+                    queue.push_back(node.borrow().right.clone());
+                }
+            }
+            res.push((sum as f64) / len as f64);
+        }
+        res
+    }
+}
+```
+
 # 429.N叉树的层序遍历
 
 [力扣题目链接](https://leetcode.cn/problems/n-ary-tree-level-order-traversal/)
@@ -1456,6 +1528,54 @@ object Solution {
 }
 ```
 
+rust:
+
+```rust
+pub struct Solution;
+#[derive(Debug, PartialEq, Eq)]
+pub struct Node {
+    pub val: i32,
+    pub children: Vec<Option<Rc<RefCell<Node>>>>,
+}
+
+impl Node {
+    #[inline]
+    pub fn new(val: i32) -> Node {
+        Node {
+            val,
+            children: vec![],
+        }
+    }
+}
+
+use std::cell::RefCell;
+use std::collections::VecDeque;
+use std::rc::Rc;
+impl Solution {
+    pub fn level_order(root: Option<Rc<RefCell<Node>>>) -> Vec<Vec<i32>> {
+        let mut res = vec![];
+        let mut queue = VecDeque::new();
+        if root.is_some() {
+            queue.push_back(root);
+        }
+        while !queue.is_empty() {
+            let mut temp = vec![];
+            for _ in 0..queue.len() {
+                let node = queue.pop_front().unwrap().unwrap();
+                temp.push(node.borrow().val);
+                if !node.borrow().children.is_empty() {
+                    for n in node.borrow().children.clone() {
+                        queue.push_back(n);
+                    }
+                }
+            }
+            res.push(temp)
+        }
+        res
+    }
+}
+```
+
 # 515.在每个树行中找最大值
 
 [力扣题目链接](https://leetcode.cn/problems/find-largest-value-in-each-tree-row/)
@@ -1686,6 +1806,38 @@ object Solution {
 }
 ```
 
+rust:
+
+```rust
+use std::cell::RefCell;
+use std::collections::VecDeque;
+use std::rc::Rc;
+impl Solution {
+    pub fn largest_values(root: Option<Rc<RefCell<TreeNode>>>) -> Vec<i32> {
+        let mut res = vec![];
+        let mut queue = VecDeque::new();
+        if root.is_some() {
+            queue.push_back(root);
+        }
+        while !queue.is_empty() {
+            let mut max = i32::MIN;
+            for _ in 0..queue.len() {
+                let node = queue.pop_front().unwrap().unwrap();
+                max = max.max(node.borrow().val);
+                if node.borrow().left.is_some() {
+                    queue.push_back(node.borrow().left.clone());
+                }
+                if node.borrow().right.is_some() {
+                    queue.push_back(node.borrow().right.clone());
+                }
+            }
+            res.push(max);
+        }
+        res
+    }
+}
+```
+
 # 116.填充每个节点的下一个右侧节点指针
 
 [力扣题目链接](https://leetcode.cn/problems/populating-next-right-pointers-in-each-node/)
@@ -2472,6 +2624,36 @@ object Solution {
 }
 ```
 
+rust:
+
+```rust
+use std::cell::RefCell;
+use std::collections::VecDeque;
+use std::rc::Rc;
+impl Solution {
+    pub fn max_depth(root: Option<Rc<RefCell<TreeNode>>>) -> i32 {
+        let mut queue = VecDeque::new();
+        let mut res = 0;
+        if root.is_some() {
+            queue.push_back(root);
+        }
+        while !queue.is_empty() {
+            res += 1;
+            for _ in 0..queue.len() {
+                let node = queue.pop_front().unwrap().unwrap();
+                if node.borrow().left.is_some() {
+                    queue.push_back(node.borrow().left.clone());
+                }
+                if node.borrow().right.is_some() {
+                    queue.push_back(node.borrow().right.clone());
+                }
+            }
+        }
+        res
+    }
+}
+```
+
 # 111.二叉树的最小深度
 
 [力扣题目链接](https://leetcode.cn/problems/minimum-depth-of-binary-tree/)
@@ -2716,6 +2898,39 @@ object Solution {
 }
 ```
 
+rust:
+
+```rust
+use std::cell::RefCell;
+use std::collections::VecDeque;
+use std::rc::Rc;
+impl Solution {
+    pub fn min_depth(root: Option<Rc<RefCell<TreeNode>>>) -> i32 {
+        let mut res = 0;
+        let mut queue = VecDeque::new();
+        if root.is_some() {
+            queue.push_back(root);
+        }
+        while !queue.is_empty() {
+            res += 1;
+            for _ in 0..queue.len() {
+                let node = queue.pop_front().unwrap().unwrap();
+                if node.borrow().left.is_none() && node.borrow().right.is_none() {
+                    return res;
+                }
+                if node.borrow().left.is_some() {
+                    queue.push_back(node.borrow().left.clone());
+                }
+                if node.borrow().right.is_some() {
+                    queue.push_back(node.borrow().right.clone());
+                }
+            }
+        }
+        res
+    }
+}
+```
+
 # 总结
 
 二叉树的层序遍历，**就是图论中的广度优先搜索在二叉树中的应用**，需要借助队列来实现（此时又发现队列的一个应用了）。