Merge pull request youngyangyang04#1259 from xiaofei-2020/greed24

添加（0968.监控二叉树.md）：增加typescript版本

Author: youngyangyang04

problems/0968.监控二叉树.md

@@ -476,7 +476,35 @@ var minCameraCover = function(root) {
 };
 ```
 
+### TypeScript
+
+```typescript
+function minCameraCover(root: TreeNode | null): number {
+    /** 0-无覆盖， 1-有摄像头， 2-有覆盖 */
+    type statusCode = 0 | 1 | 2;
+    let resCount: number = 0;
+    if (recur(root) === 0) resCount++;
+    return resCount;
+    function recur(node: TreeNode | null): statusCode {
+        if (node === null) return 2;
+        const left: statusCode = recur(node.left),
+            right: statusCode = recur(node.right);
+        let resStatus: statusCode = 0;
+        if (left === 0 || right === 0) {
+            resStatus = 1;
+            resCount++;
+        } else if (left === 1 || right === 1) {
+            resStatus = 2;
+        } else {
+            resStatus = 0;
+        }
+        return resStatus;
+    }
+};
+```
+
 ### C 
+
 ```c
 /*
 **函数后序遍历二叉树。判断一个结点状态时，根据其左右孩子结点的状态进行判断