Insertion Sort List

Insertion Sort List

Sort a linked list using insertion sort.

这道题用两个链表做的，这样方便一点。还有新链表头结点我没有存放内容，这样也比较方便，后面返回head1.next就好了

/**
 * 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 head1 = new ListNode(0);
        if(null == head || null == head.next)
            return head;
        
        else{            
            ListNode temp = new ListNode(0);
            temp.val = head.val;
            temp.next = null;
            head1.next = temp;//用一个新链表
            
            ListNode ptr = head.next;
            while(ptr != null){        //遍历原来的链表，插入到新链表中
                temp = head1.next;
                ListNode tempPre = head1;            //temp前面的节点
                while(temp != null){
                    if(temp.val > ptr.val){            //在temp前面插入结点
                        ListNode nodeAdd = new ListNode(0);
                        nodeAdd.val = ptr.val;
                        nodeAdd.next = temp;
                        tempPre.next = nodeAdd;
                        break;                        //插入完成，跳出循环
                    }
                    temp = temp.next;
                    tempPre = tempPre.next;
                }
                if(null == temp){                    //在新链表添加节点
                    ListNode nodeAdd = new ListNode(0);
                    nodeAdd.val = ptr.val;
                    nodeAdd.next = null;
                    tempPre.next = nodeAdd;
                }
                ptr = ptr.next;
            }
        }
        
        return head1.next;
    }
}