question: student_link

现有男女学生链表（链表结点中有名字和年龄两个元素）：①将 男学生链表 和 女学生链表按年龄从小到大合并，②将合并后的链表逆序排列，③通过年龄能搜索到该年龄的学生的姓名。

#include 
#include 
#include 
#include 
#define MAX_SIZE 20
struct student
{
   int age;
   char name[MAX_SIZE];
   struct student* next;
};

typedef struct student Stu;
typedef Stu* Link;

void init(Link* head)
{
    *head = (Link)malloc(sizeof(Stu));
    (*head)->next = *head;
}
void insert_tail_node(Link head,Link newnode)
{
    Link temp = head;
    while(temp->next != head)
    {
        temp = temp->next;
    }
    temp->next = newnode;
    newnode->next = head;
}

void display(Link head)
{
    Link temp = head->next;
    while(temp != head)
    {
        printf("%d %s ",temp->age,temp->name);
        temp = temp->next;
    }
}

int sort_insert(Link head,Link newnode)
{   Link temp = head;
    Link front = temp;
    temp = temp->next;
    while(temp != head)
    {
        if(temp->age >= newnode->age)
        {
            newnode->next = front->next;
            front->next = newnode;
            return 0;
        }
        front = temp;
        temp = temp->next;
    }
    newnode->next = front->next;
    front->next = newnode;
    return 0;
}

Link combine_link(Link head1,Link head2)
{
    Link head;
    Link temp1 = head1->next;
    Link temp2 = head2->next;
    Link newnode = NULL;

    init(&head);

    while(temp1 != head1)
    {
        newnode = (Link)malloc(sizeof(Stu));
        newnode->age = temp1->age;
        strcpy(newnode->name,temp1->name);

        sort_insert(head,newnode);
        temp1 = temp1->next;
    }
    while(temp2 != head2)
    {
        newnode = (Link)malloc(sizeof(Stu));
        newnode->age = temp2->age;
        strcpy(newnode->name,temp2->name);

        sort_insert(head,newnode);
        
        temp2 = temp2->next;
    }
    return head;
}
int reverse_link(Link* head)
{
    if((*head)->next == NULL || (*head)->next->next == NULL)
    {
        return 0;
    }
    else
    {
        Link p = *head;
        Link s = p->next;
        Link t = s->next;
        while(t != *head)
        {
            s->next = p;
            p = s;
            s = t;
            t = t->next;
        }
        s->next = p;
        (*head)->next = s;
        return 0;
    }
}
int search(Link head,int age)
{
    Link temp = head;
    Link front = temp;
    temp = temp->next;
    int flag = 0;
    while(temp != head)
    {
        if(temp->age == age)
        {
            printf("%s\n",temp->name);
            flag = 1;
        }
        temp = temp->next;
    }
    if(flag == 1)
    {
        return 0;
    }
    else
    {
        temp = head;
        front = temp;
        temp = temp->next;
        while(temp != head)
        {
        if(age > temp->age)
        {
            if(fabs(front->age - age) > fabs(temp->age - age))
            {
                printf("%s\n",temp->name);
                return 0;
            }
            else if(fabs(front->age - age) < fabs(temp->age - age))
            {
                printf("%s\n",front->name);
                return 0;
            }
            else
            {
                printf("%s\n",front->name);
                printf("%s\n",temp->name);
                return 0;
            }
        }
        front = temp;
        temp = temp->next;
        }
   }    
   return 0;
}
int main()
{
    Link b_head;
    Link g_head;
    Link head;
    Link newnode;

    init(&b_head);
    init(&g_head);
    init(&head);

    Stu boy[3] = {{11,"caozeren"},{10,"shenyuhui"},{12,"wangrenze"}};
    Stu girl[3] = {{19,"zhenchen"},{18,"xuweijuan"},{20,"zhuhuiyu"}};
    
    int i = 0;
    for(i = 0; i < 3; i++)
    {
        newnode = &boy[i];
        insert_tail_node(b_head,newnode);
    }
    for(i = 0; i < 3; i++)
    {
        newnode = &girl[i];
        insert_tail_node(g_head,newnode);
    }
    display(b_head);
    printf("\n");

    display(g_head);
    printf("\n");

    head = combine_link(b_head,g_head);
    display(head);
    printf("\n");

    reverse_link(&head);
    display(head);

    search(head,17);

    return 0;
}