雙向鏈表實現插入，遍歷，查詢，排序功能

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
typedef struct stu
{
	//數據域
	int num;
	char name[32];
	int age;

	//指針域
	struct stu *next;
	struct stu *pre;

}STU;
extern STU* link_insert(STU *head,STU tmp);
extern void link_print(STU *head);
extern void link_search(STU *head);
extern STU* link_sort(STU *head);
int main(int argc,char *argv[])
{ 
	char cmd[32];
	STU *head=NULL;
	STU tmp;


	
	while(1)
	{
		//來個指令
		printf("請輸入指令:");
		scanf("%s",cmd);

		//指令的情況分一分
		if(strcmp(cmd,"insert")==0)
		{
			//頭部插入
			//插入數據
			printf("請輸入要插入的數據：\n");
			scanf("%d%s%d",&tmp.num,tmp.name,&tmp.age);
			
			head=link_insert(head,tmp);
		}
		else if(strcmp(cmd,"print")==0)
		{
			//雙向遍歷
			link_print(head);
		}
		else if(strcmp(cmd,"search")==0)
		{
			//找一找
			link_search(head);
		}
		else if(strcmp(cmd,"sort")==0)
		{
			//排個序吧
			head=link_sort(head);
		}

		else if(strcmp(cmd,"quit")==0)
			break;
	}
	


	return 0;
}

//一個簡單的頭部插入函數
STU* link_insert(STU *head,STU tmp)
{
	STU *pi=NULL;
	//1、爲數據申請一個堆區空間吧
	pi=(STU *)calloc(1,sizeof(STU));

	//2、將tmp的數據賦給pi
	*pi=tmp;

	//3、鏈表不存在時
	if(NULL==head)
	{
		head=pi;
		head->next=head;
		head->pre=head;
	}

	//4、鏈表存在（挺複雜的）
	else
	{
		pi->next=head;
		pi->pre=head->pre;
		pi->pre->next=pi;
		head->pre=pi;
		head=pi;
		
	}
	return head;
	
}


//一個複雜的雙向遍歷函數
void link_print(STU *head)
{
	if(NULL==head)//這該死的鏈表還沒寫呢
	{
		printf("link not found!!!");
		return ;
	}
	else//鏈表找到了
	{
		STU *pb=head;//頭
		STU *pf=head->pre;//尾
		printf("雙向遍歷的結果哦！\n");
		do
		{
			if(pb==pf)//頭尾合一
			{
				printf("%d %s %d \n",pb->num,pb->name,pb->age);//打印一個
				break;
			}
			printf("%d %s %d \n",pb->num,pb->name,pb->age);
			printf("%d %s %d \n",pf->num,pf->name,pf->age);
			pb=pb->next;//移動
			pf=pf->pre;//我也來
		}
		while(pb->pre != pf);
		
	}
	return;
}


//簡單的查找函數
void link_search(STU *head)
{
	//鏈表不存在的情況
	if(NULL==head)
	{
		printf("link not found!!!\n");
		return;
	}
	else//鏈表存在
	{
		STU *pi=head;
		STU *pb=head->pre;
		char name[32];
		printf("請輸入要查找的節點名字：");
		scanf("%s",name);

		//查找
		do
		{
			if(strcmp(name,pi->name) == 0 )//pi找到了name
			{
				printf("%d %s %d \n",pi->num,pi->name,pi->age);
				break;
			}
			else if(strcmp(name,pb->name) == 0)//pb找到了name
			{
				printf("%d %s %d \n",pb->num,pb->name,pb->age);
				break;
			}
			pi=pi->next;//我往後移
			pb=pb->pre;//我往前移動
		}
		while(pb !=pi && pi->pre != pb);//不相遇，不相等

		
	}
	return;

}


//排序函數
STU* link_sort(STU *head)
{
	//鏈表不存在的情況
	if(NULL==head)
	{
		printf("link not found!!!\n");
		return head;
	}
	else//鏈表存在，用選擇排序法來搞
	{
		STU *p_i=head;
		STU *pb=head;
		while(p_i->next!=pb)//外層循環
		{
			STU *p_min=p_i;
			STU *p_j=p_min->next;
			while(p_j != pb)//內層循環
			{
				if(p_min->num > p_j->num)
					p_min = p_j;//最小值
				p_j = p_j->next;//右移		
			}
			if(p_min != p_i)//排序
			{
				//整體交換
				STU tmp;
				tmp = *p_i;
				*p_i = *p_min;
				*p_min = tmp;	
			
				//指針域交換回來
				tmp.next = p_i->next;
				tmp.pre = p_i->pre;		
				p_i->next = p_min->next;
				p_i->pre = p_min->pre;
				p_min->next = tmp.next;
				p_min->pre = tmp.pre;
			}
			p_i = p_i->next;//外層右移
		}
		
	}
		return head;
}

運行結果：