[LeetCode] Insertion Sort List

Sort a linked list using insertion sort.

Solution:

新建链表，逐个插入即可~

/**

 * Definition for singly-linked list.

 * struct ListNode {

 *     int val;

 *     ListNode *next;

 *     ListNode(int x) : val(x), next(NULL) {}

 * };

 */

class Solution {

public:

    ListNode *insertionSortList(ListNode *head) {

        if(head == NULL || head -> next == NULL) 

            return head; //0 and 1 nodes return itself

        

        ListNode *sortedHead = new ListNode(head -> val), *srcNode = head -> next;

        while(srcNode != NULL)

        {

            ListNode *preNode = NULL, *curNode = sortedHead;

             while(curNode != NULL)

            {

                if(curNode -> val < srcNode -> val)

                 {

                     preNode = curNode;

                        curNode = curNode -> next;

                }

                else

                    break;

            }

            if(preNode != NULL)

            {

                preNode -> next = new ListNode(srcNode -> val);

                preNode -> next -> next = curNode;

            }

            else

            {

                ListNode *tmp = sortedHead;

                sortedHead = new ListNode(srcNode -> val);

                sortedHead -> next = tmp;

            }

            srcNode = srcNode -> next;

        }

        

        return sortedHead;

    }

};