帶頭結點的連結串列及選單 2018年12月26日
以下內容僅供娛樂，歡迎隨時探討，請多指教！

#include<stdio.h>
#include<stdlib.h>
#include<conio.h>
/*定義結構體*/
struct student {
	int num;
	float score;
	struct student *next;
};
/*初始化連結串列*/
struct student *Init_List() {
	struct student *head;
	head=(struct student*)malloc(sizeof
 
 (struct student) );
	if(head==NULL) {           //小心別漏這個
		printf("申請頭結點失敗!\n");
		return NULL;
	}
	head->next=NULL;
	return head;
}
/*建立帶頭結點的連結串列*/
struct student *create_head(struct student *head) {
	int sno;
	float score;
	struct student *p,*q;
	q=head;
	while(q->next) q=q->next;
	printf("請輸入學號和成績，學號輸入-1結束: "
 
);
	scanf("%d%f",&sno,&score);
	while(sno>=0) {
		p=(student *)malloc(sizeof(student));
		p->num=sno;
		p->score=score;
		q->next=p;
		q=p;
		scanf("%d%f",&sno,&score);
	}
	q->next=NULL;
	return head;
}
/*將s指向的結點插入連結串列,使連結串列保持升序,並返回頭結點*/
void insert(struct student *head,struct
 
 student *s) {
	struct student *p=head;
	while(p->next!=NULL&&s->score>p->next->score)//特別注意&&左右不能寫反,若s最大,最後p->next=NULL,p->next->score執行出錯
		p=p->next;
	if(p->next==NULL) { //s->score最大的情況     //其實兩種情況可以並在一塊寫
		p->next=s;    //連線結點
		s->next=NULL;   //p->next就等於NULL
	} else {
		s->next=p->next;
		p->next=s;    //連線結點,這兩條語句不要寫反

	}
}
/*查詢符合條件的結點,並返回指向該結點的指標*/
struct student * search(struct student *head,int num) {
	struct student *p=head->next;
	while(p!=NULL&&p->num!=num)   //特別注意兩條件不能寫反,若寫反最後p指向NULL時p->num找不到 執行出錯
		p=p->next;
	return p;
}
/*輸出連結串列各結點的值,也稱對連結串列的遍歷*/
void print(struct student *head) {
	struct student *p;
	printf("  連結串列如下:  \n");
	p=head->next;
	while(p) {
		printf("%d\t%.1f\n",p->num,p->score);
		p=p->next;
	}
}
/*釋放連結串列*/
void free_list(struct student *head) {
	struct student *p=head ;
	printf("釋放連結串列:\n");
	while(p!=NULL) {
		head=head->next;
		free(p);
		p=head;
	}
	printf("釋放連結串列成功!\n");
}
/*刪除連結串列中值為num的結點,並返回連結串列的首指標*/
void delete_note(struct student *head,int num_x) {
	struct student *p1=head->next , *p2=head ;
	while(p1!=NULL&&p1->num!=num_x) { //特別注意&&左右條件不能調換,若調換如果p1指向NULL時p1->num執行出錯
		p2=p1;
		p1=p1->next;
	}
	if(p1==NULL)    return;

	p2->next=p1->next;
	free(p1);

}
//獲取連結串列長度（不包括頭節點）
int Size_List(struct student* head) {
	struct student* temp = head->next;
	int size = 0;
	while (temp) {
		size++;
		temp = temp->next;
	}
	return size;
}
//連結串列的排序（冒泡）
void Sort_List(struct student* head) {
	int i,j, n = Size_List(head);
	struct student *p;
	int t;
	float r;
	for (i=1; i<n; i++) {
		p=head->next;
		for (j=1; j<=n-i; j++) {
			if (p->score > p->next->score) {
				t=p->num,p->num=p->next->num,p->next->num=t;
				r=p->score,p->score=p->next->score,p->next->score=r;
			}
			p=p->next;
		}
	}
}
/*完整的有頭結點連結串列操作程式*/
int main() {
	struct student *p , *head ;
	char c;
	int num ;
	float score ;
	printf("有頭結點連結串列操作程式:\n");
	head=Init_List();
	while(1) {
		printf("\nC:建立連結串列 I:插入結點(自動升序)  P:輸出連結串列 "
		" S:查詢結點  D:刪除結點  X:排序 E:釋放連結串列並退出程式! \n ");
		c=getch();
		switch(c) {
			case 'I':
			case 'i':
				printf("請分別輸入要插入學生的學號和分數:\n");
				scanf("%d%f",&num,&score);
				p=(struct student*)malloc( sizeof(struct student) );
				if(p==NULL) {
					printf("申請該結點失敗!!!\n");
					exit (0) ;
				}
				p->num=num;
				p->score=score;   //給p賦值
				insert(head,p);
				printf("插入成功!\n");
				break;
			case 'C':
			case 'c':
				head=create_head(head);
				break;
			case'P':
			case 'p':
				print(head);
				break;
			case'S':
			case 's':
				printf("輸入要查詢的學號\n");
				scanf("%d",&num);
				p=search(head,num);
				if (p) {
					printf("該學生資訊為： ");
					printf("num=%d,score=%f\n",p->num,p->score);
				} else
					printf("該學生不存在\n");
				break;
			case'D':
			case 'd':
				printf("請輸入要刪除的學生的學號:\n");
				scanf("%d",&num);
				delete_note(head,num);
				break;
			case 'X':
			case 'x':
				Sort_List(head);
				break;
			case 'E':
			case 'e':
				free_list(head);
				exit (0);
		}
	}
	return 0;
}