逆轉鏈表

每次我都不想接觸鏈表和樹的操作

鏈表結構
/**
 * Definition for singly-linked list.
 * function ListNode(val) {
 *     this.val = val;
 *     this.next = null;
 * }
 */

這次要求逆轉鏈表結構(javascript)

核心思想是通過先存儲鏈表當前節點的next數據  --------- let tt = tem.next;

使當前的節點的next指向我們設置的新鏈表（開始為null）---------------tem.next = newhead;

更新新鏈表 ---------------------newhead = tem;

更新舊鏈表準備下一次迴圈 ----------------------tem = tt;

 1  /**
 2  * @param {ListNode} head
 3  * @return {ListNode}
 4  */
 5 var reverseList = function(head) {
 6         if(head === null){
 7             return null;
 8         }
 9         let newhead = null;
10         let tem = head;
11         while (tem != null){
12             let tt = tem.next;
13             tem.next = newhead;
14             newhead = tem;
15             tem = tt;
16         }
17         return newhead;
18 };