其实暴力遍历开数组也可以，但不如以下新建链表块的方法简单

int FindCommDivisor(int num1, int num2)
{
    int n;
    int i;
    n = fmin(num1, num2);
    for (i = n; i >= 1; i--) {
        if (num1 % i == 0 && num2 % i == 0) {
            return i;
        }
    }
    return 0;
}

struct ListNode *insertGreatestCommonDivisors(struct ListNode *head)
{
    struct ListNode *p1 = head;
    while (p1->next) {
        struct ListNode *node = malloc(sizeof(struct ListNode));   
        node->val = FindCommDivisor(p1->val, p1->next->val);
        node->next = p1->next;
        p1->next = node;
        p1 = node->next;
    }
    return head;
}