Merge pull request #1007 from xiaofei-2020/ts4

添加（0024.两两交换链表中的节点.md）：增加typescript版本

problems/0024.两两交换链表中的节点.md

@@ -250,6 +250,38 @@ var swapPairs = function (head) {
 };
 ```
 
+TypeScript：
+
+```typescript
+function swapPairs(head: ListNode | null): ListNode | null {
+    /**
+     * 初始状态：
+     * curNode -> node1 -> node2 -> tmepNode
+     * 转换过程：
+     * curNode -> node2
+     * curNode -> node2 -> node1
+     * curNode -> node2 -> node1 -> tempNode
+     * curNode = node1
+     */
+    let retNode: ListNode | null = new ListNode(0, head),
+        curNode: ListNode | null = retNode,
+        node1: ListNode | null = null,
+        node2: ListNode | null = null,
+        tempNode: ListNode | null = null;
+
+    while (curNode && curNode.next && curNode.next.next) {
+        node1 = curNode.next;
+        node2 = curNode.next.next;
+        tempNode = node2.next;
+        curNode.next = node2;
+        node2.next = node1;
+        node1.next = tempNode;
+        curNode = node1;
+    }
+    return retNode.next;
+};
+```
+
 Kotlin:
 
 ```kotlin