题目：链表插入排序

用插入排序对链表排序

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样例

Given 1->3->2->0->null, return 0->1->2->3->null

标签 Expand

排序 链表

相关题目 Expand

方法1：将所有的链表的val排序，然后重新新建链表

/**
* Definition for ListNode.
* public class ListNode {
*     int val;
*     ListNode next;
*     ListNode(int val) {
*         this.val = val;
*         this.next = null;
*     }
* }
*/
public class Solution {
    /**
     * @param head: The first node of linked list.
     * @return: The head of linked list.
     */
    public ListNode insertionSortList(ListNode head) {
        // write your code here
        if(head==null||head.next==null) return head;
         ListNode cur = head;
         ArrayList iList = new ArrayList<>();
         while(cur!=null){
              iList.add(cur.val);
              cur = cur.next;
         }
         Collections.sort(iList);
         ListNode xhead = new ListNode(iList.get(0));
         ListNode x = xhead;
         for(int i=1;i               x.next = new ListNode(iList.get(i));
              x = x.next;
         }
        
        return xhead;
    }
}

方法2：每次循环找到一个元素在当前排好的结果中相对应的位置，然后插进去，经过n次迭代之后就得到排好序的结果了。O（n^2）的时间复杂度

/**
* Definition for ListNode.
* public class ListNode {
*     int val;
*     ListNode next;
*     ListNode(int val) {
*         this.val = val;
*         this.next = null;
*     }
* }
*/
public class Solution {
    /**
     * @param head: The first node of linked list.
     * @return: The head of linked list.
     */
    public ListNode insertionSortList(ListNode head) {
        // write your code here
        if(head==null||head.next==null) return head;
        ListNode newx = new ListNode(0);
        ListNode cur = head;
        ListNode newcur = newx;
        while(cur!=null){
             ListNode curnext  = cur.next;
             newcur  = newx;
             while(newcur.next!=null&&newcur.next.val                   newcur = newcur.next;
             }
             cur.next = newcur.next;
             newcur.next = cur;
             cur = curnext;            
        }
        return newx.next;
    }
}