LeetCode Insertion Sort List

class Solution {

public:

    ListNode *insertionSortList(ListNode *head) {

        if (head == NULL) return NULL;

        ListNode* sorted_head = head;

        ListNode* unsorted_head = head->next;

        head->next = NULL;

ListNode* cur = unsorted_head;
while (cur != NULL) {

            unsorted_head = cur->next;

            cur->next = NULL;

            sorted_head = insertNode(sorted_head, cur);

            cur = unsorted_head;

        }
return sorted_head;

    }
ListNode* insertNode(ListNode* list, ListNode* node) {

        if (list == NULL && node == NULL) return NULL;

        if (node == NULL) return list;

        if (list == NULL) return node;

        ListNode* cur = list;

        ListNode* pre = NULL;

        while (cur != NULL && cur->val < node->val) {

            pre = cur;

            cur = cur->next;

        }

        if (pre == NULL) {

            node->next = list;

            return node;

        } else {

            node->next = pre->next;

            pre->next = node;

            return list;

        }

    }

};

感觉很简单，写起来又是这错那错

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