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147. Insertion Sort List

题目

Sort a linked list using insertion sort.

解答

• 首先清楚基于数组的插入排序思路
• 处理链表操作

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode(int x) : val(x), next(NULL) {}
 * };
 */
// insertion sort list
class Solution {
public:
    ListNode *insertionSortList(ListNode *head) {
    //思路:新建一个链表, 遍历原链表，将每个节点加入新链表正确的位置

        ListNode* dummy = new ListNode(0);
        ListNode* cur = head; //原链表当前位置
        ListNode* next = NULL;  //记录原链表下一节点
        ListNode* pre = dummy; //新链表需要比较的前后节点

        while (cur)
        {
            next = cur->next;
            while (pre->next&& pre->next->val < cur->val)
            {
                pre = pre->next;
            }

            cur->next = pre->next; //将当前节点独立出来
            pre->next = cur;
            pre = dummy; //回到起点

            cur = next;    //处理下一个节点
        }
        return dummy->next;
    }
};

题目来源：147. Insertion Sort List