Merge pull request youngyangyang04#1003 from xiaofei-2020/ts2

添加（0206.翻转链表.md）：增加typescript版本

Author: youngyangyang04

problems/0206.翻转链表.md

@@ -314,6 +314,54 @@ var reverseList = function(head) {
 };
 ```
 
+TypeScript:
+
+```typescript
+// 双指针法
+function reverseList(head: ListNode | null): ListNode | null {
+    let preNode: ListNode | null = null,
+        curNode: ListNode | null = head,
+        tempNode: ListNode | null;
+    while (curNode) {
+        tempNode = curNode.next;
+        curNode.next = preNode;
+        preNode = curNode;
+        curNode = tempNode;
+    }
+    return preNode;
+};
+
+// 递归（从前往后翻转）
+function reverseList(head: ListNode | null): ListNode | null {
+    function recur(preNode: ListNode | null, curNode: ListNode | null): ListNode | null {
+        if (curNode === null) return preNode;
+        let tempNode: ListNode | null = curNode.next;
+        curNode.next = preNode;
+        preNode = curNode;
+        curNode = tempNode;
+        return recur(preNode, curNode);
+    }
+    return recur(null, head);
+};
+
+// 递归（从后往前翻转）
+function reverseList(head: ListNode | null): ListNode | null {
+    if (head === null) return null;
+    let newHead: ListNode | null;
+    function recur(node: ListNode | null, preNode: ListNode | null): void {
+        if (node.next === null) {
+            newHead = node;
+            newHead.next = preNode;
+        } else {
+            recur(node.next, node);
+            node.next = preNode;
+        }
+    }
+    recur(head, null);
+    return newHead;
+};
+```
+
 Ruby:
 
 ```ruby