rust 968 min camera cover version 2

problems/0968.监控二叉树.md

@@ -626,6 +626,42 @@ impl Solution {
     }
 }
 
+/// 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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