finish Problem 24

完善了README，给程序添加了注释

Author: aQua

Algorithms/0024.swap-nodes-in-pairs/README.md

@@ -9,7 +9,7 @@ Given 1->2->3->4, you should return the list as 2->1->4->3.
 Your algorithm should use only constant space. You may not modify the values in the list, only nodes itself can be changed.
 
 ## 解题思路
-
+利用递归，可以简介明了完成程序。详见程序注释。
 
 ## 总结
 

Algorithms/0024.swap-nodes-in-pairs/swap-nodes-in-pairs.go

@@ -11,9 +11,13 @@ func swapPairs(head *ListNode) *ListNode {
 		return head
 	}
 
-	t := head.Next
-	head.Next = swapPairs(t.Next)
-	t.Next = head
+	// 让temp指向head.Next节点
+	temp := head.Next
+	// 让head.Next指向转换好了temp.Next节点
+	head.Next = swapPairs(temp.Next)
+	// 让temp.Next指向head节点
+	temp.Next = head
+	// temp成为新的head节点
 
-	return t
+	return temp
 }