C语言 单向链表 及其排序

#include<stdio.h>
#include<malloc.h>
#define LEN sizeof(struct Student)
struct Student                //结构体声明
{
  long num;
  int score;
  struct Student* next;
 };
 int n; 

struct Student* creat()           //创建单向链表
{
	 struct Student *head=NULL, *p_before, *p_later;
 	 p_before = p_later = (struct Student*) malloc(LEN);
 	 scanf_s("%ld%d", &p_before->num, &p_before->score);
 	 while (p_before->num!=0)
 	 {
 	 	n++;
 	 	if (n == 1)
 	 	 	head = p_before;
	    else 
	    	p_later->next = p_before;
	    p_later = p_before;
	    p_before = (struct Student*) malloc(LEN);
	    scanf_s("%ld%d", &p_before->num, &p_before->score);
	  }
	  p_later->next = NULL;
	  free(p_before);
	  return head;
 } 

struct Student* sort(struct Student* list)               //冒泡排序，
{                                                                           
  struct Student *p, *q;
  int temp1,i;
  long temp2;
  for (p = list, i =1; i < n;i++,p=p->next)
  	 for (q = p->next;q!= NULL;q=q->next)  
  		  if (p->score < q->score)
		    {
		     temp1 = p->score;
		     p->score = q->score;
		     q->score = temp1;
		     temp2 = p->num;
		     p->num = q->num;
		     q->num = temp2;
		    }
    return list;
 } 

struct Student* sort1(struct Student* h)                //插入排序   
 {                                                                           
 struct Student *f, *t, *p=NULL, *q;
  f = h->next;                  
 h->next = NULL;              
 while (f!=NULL)   
 {
   for (t = f, q = h; (q != NULL && (q->score > t->score)); p = q, q = q->next);
                          
  f = f->next;         //在进行插入操作前，先使f后移
  if (q == h) h = t;   //如果当前新链的头节点关键值比f（即t）所指节点关键值小，需要将f（即t）所指节点插在该头节点前，先让新链头节点指针指向
                       //f（即t）所指节点，作为新链的新的头节点
  else  p->next = t;   //否则，将f（即t）所指节点连在p所指节点后
  t->next = q; //不管if还是else，都需要将f（即t）所指节点连在q所指节点前，如果q=NULL，就是让f（即t）所指节点的next域指向NULL,这显然也是正确的
 }
  return h;  //返回新链（排好序的链）的头节点指针
} 

struct Student* sort2(struct Student* h)                                                 //选择排序
{                                                                                                             
  struct Student *f=NULL,*t=NULL, *max, *maxbf=NULL, *p;                 

 while (h!=NULL)                                                                                   
  {
   for (p = h, max = h; p->next != NULL; p = p->next)
   {
    if (p->next->score > max->score)
    {
     maxbf = p;
     max = p->next;
    }
   }
   if (f==NULL)
   {
    f = max;
    t = max;
   }
   else
   {
    t->next = max;
    t = max;
   }
   if (max==h)
   {
    h = h->next;
   }
   else
   {
    maxbf->next = max->next;
   }
  }
  t->next = NULL;
  return f;
 } 

struct Student* sort3(struct Student* h)                                            //这是什么排序呢？我也说不好。这是我自己想出来的算                                                                               
 {                                                                                                        //法……大体思想是：先从链表第一个结点开始遍历链表，找出关键值（这里是成绩score）最大的（因为
 struct Student *p, *q, *pt=NULL, *pbf=NULL, *qbf=NULL;              //是从大到小排序）结点和链表中第一个结点交换（利用指针实现）；然后，从链表中第二个结点开始遍历链
 for (p = h ; p->next!=NULL; pbf = p, p = p->next)                           //表，找出关键值最大的结点和链表中第二个结点交换……如此操作，直到从链表中最后一个结点开始的那趟
 {                                                                                                      //遍历和操作结束
  for (q = p; q->next != NULL;q=q->next)                                         //代码格式很不好，写这段代码时在下还很渣很渣……粘贴到这里时，就更不好看了……对不起大家了
  { 

   if (p->score < q->next->score)
    {
     qbf = q; q = q->next;
     if (p==h && p->next==q)
     {
      h = q; p->next = q->next; q->next = p; p = q;
     }
     else
     {
      if (p == h&&p->next != q)
      {
       h = q; pt = q->next; q->next = p->next, qbf->next = p; p->next = pt; p = q; q = qbf;
      }
      else
      {
       if (p != h && p->next == q)
       {
        pt = q->next; pbf->next = q; q->next = p; p->next = pt; p = q;
       }
       else
       {
        if (p != h && p->next != q)
        {
         pt = q->next; pbf->next = q; q->next = p->next; qbf->next = p; p->next = pt; p = q; q = qbf;
        }
       }
      }
     }
    }
   }
  }
  return h;
 } 




//快排    这里在下也参考了网上的代码，但在下也着实进行了一番改进才编译通过，这里使用了指针的指针，不详细讲了，大家自己分析吧 

struct Student* Link_Quick_Sort(struct Student ** head, struct Student ** end)          //  注意这里函数返回值可以写成void，同时将return语句去掉，
{                                                                                       //同时，将main函数中(1)(2)两句改为：
 struct Student * big_head=NULL, *big_end=NULL, *small_head=NULL, *small_end=NULL;   //Link_Quick_Sort(&pt, NULL);
  struct Student * big_tail=NULL, *small_tail = NULL;                                 //for (p=pt, i = 1; i <= n; i++, p = p->next)
  int key = (*head)->score;                              //也是可以的。原因是递归是先进后出，后进先出，二第一次调用时传的是&pt（见main函数中
 struct Student * traversal = (*head)->next;            //第(1)句），故当整个函数结束后，pt的值已修改，且指向排好序的链表的头结点。
 (*head)->next = NULL;                                  
  struct Student *p = NULL;
  while (traversal != NULL)
  {
   if (traversal->score > key)
   {
    if (big_head == NULL) { big_head = traversal; big_tail = traversal; }
    else{ big_tail->next = traversal; big_tail = traversal; }
    traversal = traversal->next;
    big_tail->next = NULL;
   }
   else
   {
    if (small_head == NULL) { small_head = traversal; small_tail = traversal; }
    else{ small_tail->next = traversal; small_tail = traversal; }
    traversal = traversal->next;
    small_tail->next = NULL;
   }
  }
   big_end = big_tail; small_end = small_tail;
   if (big_head != NULL && big_head->next != NULL){ Link_Quick_Sort(&big_head, &big_end); }
   if (small_head != NULL && small_head->next != NULL){ Link_Quick_Sort(&small_head, &small_end); }
   if (big_end != NULL&&small_head != NULL)
   {
    big_end->next = (*head);
    (*head)->next = small_head;
    (*head) = big_head; 
    if (end == NULL){ end = &p; }
    (*end) = small_end;
   }
   else if (big_end!=NULL)
   {
    big_end->next = (*head); 
    if (end == NULL){  end = &p; }
    (*end) = (*head); 
    (*head) = big_head;
   }
   else if (small_head!=NULL)
   {
    (*head)->next = small_head; 
    if (end == NULL){ end = &p; }
    (*end) = small_end;
   }
   return (*head);
 } 

void main()                                                   //用main函数来测试
{
  printf("请依次输入学生的学和姓名\n");
  printf("学号和姓名间以空格隔开\n");
  printf("输入0 0结束\n");
  struct Student* pt,*p;
  struct Student* creat();
  struct Student* sort();               //这里调用的是冒泡排序，要想调用其它排序，在这里改一下函数调用就可以了
 pt=creat();
  int i;
  for ( p=pt,i = 1; i <=n; i++,p=p->next)
   printf("num=%ld score=%d\n", p->num, p->score);
  printf("排序后：\n");
     p=Link_Quick_Sort(&pt, NULL);     //(1)
  for ( i = 1; i <= n; i++, p = p->next)//(2)
   printf("第%d名： num=%ld score=%d\n",i, p->num, p->score);
 }