Merge pull request #1818 from MIracleyin/master

添加 968 监控二叉树 Rust 版本

problems/0968.监控二叉树.md

@@ -577,6 +577,91 @@ object Solution {
     result
   }
 }
+```
+### Rust
+```Rust
+/// 版本一
+impl Solution {
+    pub fn min_camera_cover(root: Option<Rc<RefCell<TreeNode>>>) -> i32 {
+        let mut res = 0;
+        if Self::traversal(&root, &mut res) == 0 {
+            res += 1;
+        }
+        res
+    }
+
+    pub fn traversal(cur: &Option<Rc<RefCell<TreeNode>>>, ans: &mut i32) -> i32 {
+        // 0 未覆盖 1 节点已设置摄像头 2 节点已覆盖
+        if let Some(node) = cur {
+            let node = node.borrow();
+
+            let left = Self::traversal(&node.left, ans);
+            let right = Self::traversal(&node.right, ans);
+
+            // 左右节点都被覆盖
+            if left == 2 && right == 2 {
+                return 0; // 无覆盖
+            }
+
+            // left == 0 right == 0 左右无覆盖
+            // left == 0 right == 1 左节点无覆盖 右节点有摄像头
+            // left == 1 right == 0 左节点有摄像头 左节点无覆盖
+            // left == 0 right == 2 左节点无覆盖 右节点有覆盖
+            // left == 2 right == 0 左节点有覆盖 右节点无覆盖
+            if left == 0 || right == 0 {
+                *ans += 1;
+                return 1;
+            }
+
+            // left == 1 right == 1 左节点有摄像头 右节点有摄像头
+            // left == 1 right == 2 左节点有摄像头 右节点覆盖
+            // left == 2 right == 1 左节点覆盖 右节点有摄像头
+            if left == 1 || right == 1 {
+                return 2; // 已覆盖
+            }
+        } else {
+            return 2;
+        }
+        -1
+    }
+}
+
+/// 版本二
+enum NodeState {
+    NoCover = 0,
+    Camera = 1,
+    Covered = 2,
+}
+
+impl Solution {
+    pub fn min_camera_cover(root: Option<Rc<RefCell<TreeNode>>>) -> i32 {
+        let mut res = 0;
+        let state = Self::traversal(&root, &mut res);
+        match state {
+            NodeState::NoCover => res + 1,
+            _ => res,
+        }
+    }
+
+    pub fn traversal(cur: &Option<Rc<RefCell<TreeNode>>>, ans: &mut i32) -> NodeState {
+        if let Some(node) = cur {
+            let node = node.borrow();
+            let left_state = Self::traversal(&node.left, ans);
+            let right_state = Self::traversal(&node.right, ans);
+            match (left_state, right_state) {
+                (NodeState::NoCover, _) | (_, NodeState::NoCover) => {
+                    *ans += 1;
+                    NodeState::Camera
+                }
+                (NodeState::Camera, _) | (_, NodeState::Camera) => NodeState::Covered,
+                (_, _) => NodeState::NoCover,
+            }
+        } else {
+            NodeState::Covered
+        }
+    }
+}
+
 ```
 
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