147. Insertion Sort List [LeetCode]

147. Insertion Sort List

鏈表排序，插入排序

class Solution {

public:

    ListNode * insertionSortList(ListNode* head) {

        if (head == nullptr || head->next == nullptr)return head;

        //創建一個系統最小節點

        ListNode dummy(INT_MIN);

        for (ListNode*cur = head; cur;) {

            auto pos = findInsertPos(&dummy, cur->val);

            //把cur節點插入pos節點之後

            ListNode*tmp = cur->next;

            cur->next = pos->next;

            pos->next = cur;

            cur = tmp;

        }

        return dummy.next;

    }

    ListNode*findInsertPos(ListNode*head, int x) {

        ListNode*pre = nullptr;

        for (ListNode*cur = head; cur&&cur->val <= x; pre = cur, cur = cur->next);

        return pre;

    }

};