添加(0541.反转字符串II.md): 增加typescript版本

problems/0541.反转字符串II.md

@@ -252,6 +252,28 @@ var reverseStr = function(s, k) {
 
 ```
 
+TypeScript：
+
+```typescript
+function reverseStr(s: string, k: number): string {
+    let left: number, right: number;
+    let arr: string[] = s.split('');
+    let temp: string;
+    for (let i = 0, length = arr.length; i < length; i += 2 * k) {
+        left = i;
+        right = (i + k - 1) >= length ? length - 1 : i + k - 1;
+        while (left < right) {
+            temp = arr[left];
+            arr[left] = arr[right];
+            arr[right] = temp;
+            left++;
+            right--;
+        }
+    }
+    return arr.join('');
+};
+```
+
 Swift:
 
 ```swift