链表插入排序



题目描述

Sort a linked list using insertion sort.

/**
 * 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) {
        if(head==null||head.next==null)
    	   return head;
       //带排序链表头结点
	   ListNode cur = head.next;
	   //已排序链表
       ListNode sort_head = new ListNode(0),location = null,location_before = null;
	   sort_head.next = head;
	   head.next = null;
       while(cur!=null){		   
		   //每次从头结点开始扫描		   
		   location_before = sort_head;
		   location = sort_head.next;
		   //找插入位置
		   while(location!=null && location.val<=cur.val){
			   location_before = location;
			   location = location.next;			   
		   }
		   //插入到排序链表中
		   location_before.next = cur;
		   cur = cur.next;
		   location_before.next.next = location;
	   }
	   return sort_head.next;
    }
}