LeetCode: Insertion Sort List 解题报告

Insertion Sort List

Sort a linked list using insertion sort.

SOLUTION:

使用一个dummynode 创建一个新的链，将旧的节点插入到新链中即可，相当简单哦！

 /**
  * Definition for singly-linked list.
  * public class ListNode {
  *     int val;
  *     ListNode next;
  *     ListNode(int x) {
  *         val = x;
  *         next = null;
  *     }
  * }
  */
 public class Solution {
     public ListNode insertionSortList(ListNode head) {
         ListNode dummy = new ListNode(0);

         while (head != null) {
             ListNode pre = dummy;

             // 注意，这里要用<= 来保证算法的稳定性
             // 因为假如有2个数相同，后面的数后找到，也要插入到后面才可以。也就是说当=的时候，是继续往下走
             while (pre.next != null && pre.next.val <= head.val) {
                 pre = pre.next;
             }

             // unlink the node from the original link. And record the next position.
             ListNode headNext = head.next;
             head.next = pre.next;

             pre.next = head;
             head = headNext;
         }

         return dummy.next;
     }
 }

GITHUB:

https://github.com/yuzhangcmu/LeetCode_algorithm/blob/master/list/InsertionSortList.java