LeetCode 之 Insertion Sort List — C++ 實現

Insertion Sort List

 

Sort a linked list using insertion sort.

對鏈表使用插入排序。

class Solution {
public:
    ListNode* insertionSortList(ListNode* head) {
        if(!head)
        {
            return NULL;
        }
        
        ListNode *tempHead = new ListNode(0);//新建臨時頭結點
        tempHead->next = head;
        
        ListNode *s = NULL, *cur = NULL;
        ListNode *pre = head, *p = head->next;
        
        while(p)
        {
            if(p->val >= pre->val)//當前節點值大於前一個節點值，則按序
            {
                p = p->next;
                pre = pre->next;
            }
            else//比前一個節點小
            {
                cur = p;
                p = p->next;
                pre->next = p;
                
                s = tempHead; //pre 重新指向表頭
                while(s->next->val < cur->val)//找到在已排好鏈表中按序所在的位置
                {
                    s = s->next;
                }
                cur->next = s->next;
                s->next = cur;
            }
        }
        
        head = tempHead->next;
        delete tempHead; //刪除臨時頭結點
        
        return head;
    }
};