147. Insertion Sort List

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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