16, to create and implement a dynamic list insert, delete, etc.

16, to create and implement a dynamic list insert, delete, etc.

Title : programming the following function and all of the following functions are organized in a C program:
(1) preparation of a function struct student * creat (void), the establishment of a data head pointer n students head for unidirectional dynamic list. Linked list node type struct student, as follows:

 struct student{ 
 		long num;    //学号  
 		int score;   //分数   
		struct student  *next;   //结点指针域
};  

(2) write a function struct student * insert (struct student * head), the head pointer is inserted a new student data for students nodes head of the linked list.
(3) Write the function struct student * del (struct student * head, long key), the head pointer list for students to remove the head of the school is the number of key nodes.
(4) Write the function int sum (struct student * head) , returns the head pointer of the list and the head student values of all nodes score.
(5) Write the function void find (struct student * head) , the output of the head pointer in the head of the list with the highest score of the student's student number and the student scores.
(6) Preparation of function void print (struct student * head) , the head pointer is the head of the output of student list of contents of all nodes.

#include<stdio.h>
#include<stdlib.h>
struct student{
	long num;
	int score;
	struct student *next;
}; 
#define LEN sizeof(struct student)	//LEN为结构体类型的存储大小   （define前要有#）
int n=0;	//n为链表结点个数 
struct student *creat(void);
struct student *insert(struct student *head);
struct student *del(struct student *head, long key);
int sum(struct student *head);
void find(struct student *head);
void print(struct student *head);

int main(){
	struct student *head, *p1, *p2;
	//学号与成绩输入“0 0”表示链表创建完成或插入结束或删除结束 
	printf("请按学号大小由小到大输入数据创建链表：\n");
	head=creat();
	
	printf("请输入插入结点的学号与成绩：\n");
	head=insert(head); 
	
	long key;
	printf("请输入要删除的结点的学号:\n");//（/与\要注意）
	scanf("%d", &key);
	head=del(head, key);
	
	printf("所有分数的和值为：%d\n",sum(head));
	//最高分的学号与成绩 
	find(head);
	//输出链表全部内容 
	print(head); 
	
	return 0;	
}
struct student *creat(void){			//创建链表的详细解释在C语言书P314 
	struct student *head, *p1, *p2;		//当结点数(n)大于1时，p2为相邻两结点的前一个结点，而p1为相邻两结点的后一个结点
	head=NULL;							//初始时没有结点，故令head为NULL 
	p2=p1=(struct student*)malloc(LEN);	//(p2=)p1=...的括号内容不能少,因为若一开始就输入0 0(即没有结点)，执行p2->next= NULL需要p2有初始指向 
	
	scanf("%ld %d", &p1->num, &p1->score);//（少了取地址符编译不会报错，但运行程序时会出错）
	while(p1->num != 0){				//注意最后要输入0 0才能结束循环 
		n++;
		if(n==1) head=p1;
			else p2->next = p1;
		p2=p1;
		p1=(struct student*)malloc(LEN);	
		scanf("%ld %d",&p1->num, &p1->score);		 
	}
	p2->next=NULL;
	return head;
}

struct student *insert(struct student *head){
	struct student *p1, *p2, *input;
	p1=head;
	input=(struct student*)malloc(LEN);
	scanf("%ld %d", &input->num, &input->score);
	
	if(head->num > input->num){
		input->next = head;				//插入到链表的表首之前 
		head=input;
	}else{
		while(p1 != NULL){
			//因不同学生的学号不可能相同，故不必考虑p1->next == input->next的情况 
			if(p1->num < input->num){
				p2=p1;
				p1=p2->next;	
			}else{
				p2->next = input;		//插入到链表之中 
				input->next = p1;
				break;					//该break很关键,不可少，否则p1不会再移动，该while循环陷入死局不断重复执行else语句 
			}
		}
	}
	if(p1 == NULL){
		p1->next = input;				//插入到链表的表尾之后 
		input->next = NULL;
	}
	return head;	
}

struct student *del(struct student *head, long key){
	struct student *p1, *p2;
	p1=head;
	
	if(head->num == key){
		head=head->next;
		n--;
	}else{
		while(p1!=NULL){
			if(p1->num == key){
				p2->next = p1->next;
				n--;
				break;
			}else{
				p2=p1;
				p1=p2->next;
			}
		} 
	}
	return head;
}

int sum(struct student *head){
	struct student *p = head;
	int s=0;
	while(p != NULL){
		s += p->score;
		p=p->next;
	}
	return s;
}

void find(struct student *head){
	struct student *p1, *p2;
	p1=p2=head;
	while(p1 != NULL){
		//假设只有一个最高分 
		if(p2->score < p1->score){
			p2=p1;
		}
		p1=p1->next;
	}
	printf("最高分为%d，该学生学号为%ld\n", p2->score, p2->num);
}

void print(struct student *head){
	struct student *p1 = head;
	printf("所有学生的学号与成绩为：\n"); 
	while(p1 != NULL){
		printf("%ld %d\n", p1->num, p1->score);
		p1=p1->next;
	}
}