[LeetCode]Insertion Sort List

最新推荐文章于 2021-11-16 15:52:48 发布

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本文介绍了一种使用C++实现的链表插入排序算法。通过定义一个虚拟头结点简化边界条件处理，遍历链表并将每个节点插入到已排序部分的适当位置。此算法适用于计算机科学和软件工程领域的数据结构课程。

/**
 * 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) {
        // IMPORTANT: Please reset any member data you declared, as
        // the same Solution instance will be reused for each test case.
        if(head == NULL) return head;
        ListNode dummy(-1);
        dummy.next = head;
        ListNode* prev = head;
        ListNode* cur = prev->next;
        while(cur)
        {
            if(cur->val >= prev->val)//greater or equal
            {
                prev = cur;
                cur = cur->next;
            }
            else//smaller
            {
                //first find the insert position
                ListNode* insertPrev = &dummy;
                ListNode* insertCur = dummy.next;
                while(insertCur->val < cur->val)
                {
                    insertPrev = insertCur;
                    insertCur = insertCur->next;
                }
                //then insert
                prev->next = cur->next;
                cur->next = insertCur;
                insertPrev->next = cur;
                cur = prev->next;
            }
        }
        return dummy.next;
    }
};