Insertion Sort List

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     struct ListNode *next;
 * };
 */
struct ListNode* insertionSortList(struct ListNode* head) {
    struct ListNode *p = head;
    struct ListNode *tmp = NULL, *min = NULL;
    int a;
    if(head == NULL)
        return NULL;
    else if(head->next == NULL)
        return head;
    while(p->next != NULL)
    {
        min = p;
        tmp = p->next;
        while(tmp != NULL)
        {
            if(tmp->val < min->val)
                min = tmp;
            tmp = tmp->next;
        }
        a = min->val;
        min->val = p->val;
        p->val = a;
        p = p->next;
    }
    return head;
}

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     struct ListNode *next;
 * };
 */
struct ListNode* insertionSortList(struct ListNode* head) {
    struct ListNode *cur = head;
    struct ListNode *helper = malloc(sizeof(struct ListNode));
    struct ListNode *pre;
    helper->next = NULL;
    if(head==NULL || head->next==NULL)
        return head;
    
    while(cur)
    {
        struct ListNode *next = cur->next;
        pre = helper;
        while(pre->next != NULL && pre->next->val < cur->val)
            pre = pre->next;
        cur->next = pre->next;
        pre->next = cur;
        cur = next;
    }
    return helper->next;
}

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     struct ListNode *next;
 * };
 */
struct ListNode* insertionSortList(struct ListNode* head) {
    struct ListNode* new_head = malloc(sizeof(struct ListNode));
    new_head -> next = head;
    struct ListNode* pre = new_head;
    struct ListNode* cur = head;
    while (cur) {
        if (cur -> next && cur -> next -> val < cur -> val) {
            while (pre -> next && pre -> next -> val < cur -> next -> val)
                pre = pre -> next;
            /* Insert cur -> next after pre.*/
            struct ListNode* temp = pre -> next;
            pre -> next = cur -> next;
            cur -> next = cur -> next -> next;
            pre -> next -> next = temp;
            /* Move pre back to new_head. */
            pre = new_head;
        }
        else cur = cur -> next;
    }
    struct ListNode* res = new_head -> next;
    free(new_head);
    return res;
}