圖的存儲方式（鄰接表）

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

typedef int datatype;
typedef struct _linknode_ {
	datatype vertex;
	struct _linknode_ *next;
}linknode;


linknode *creat_linknode(datatype value)
{
	linknode *p = (linknode *)malloc(sizeof(linknode));
	memset(p,0,sizeof(linknode));
	p->vertex = value;
}

void insert_linknode(linknode *head,datatype v)
{
	linknode *p = NULL,
			 *new = NULL;
	if (NULL == head)
		return ;
	p = head;
	while(NULL != p->next && p->next->vertex <= v)
		p = p->next;
	if(p->vertex == v)
		return ;
	new = creat_linknode(v);
	new->next = p->next;
	p->next = new;
	return ;
}

void annul_linklist(linknode *head)
{
	linknode *p = NULL;
	while(head != NULL)
	{
		p = head;
		head = head->next;
		free(p);
	}
}

int main()
{
	datatype nu;
	datatype v1 = -1,v2 = -1;
	linknode *p = NULL;
	puts("input the number of vertex:");
	while( 1 != scanf("%d",&nu))//輸入一個圖共有幾個頂點
		getchar();
	const int N = nu;
	printf("the number of vertex is : %d\n",N);
	linknode *vertexs = (linknode *)malloc(sizeof(linknode) * N);
	memset(vertexs,0,sizeof(linknode) * N);

	puts("input the relation of yout graph,like [1,2]:");//邊的輸入
	while (1)
	{
		while( 2 != scanf("%d,%d",&v1,&v2))
			getchar();
		if(v1 == v2)
			break;
		if(v1 < 0 || v1 >= N || v2 < 0 || v2 >= N)
			continue;
		insert_linknode(vertexs + v1,v2);
		insert_linknode(vertexs + v2,v1);
	}

	for(v1 = 0; v1 < N; v1 ++)
	{
		p = vertexs[v1].next;
		printf("V%d:  ",v1);
		while(NULL != p)
		{
			printf(" V%d,",p->vertex);
			p = p->next;
		}
		putchar(8);
		putchar(32);
		putchar(10);//這三個是爲了消去打印時最後留下的那個逗號
		annul_linklist(vertexs[v1].next);//最後進的清空
	}

	free(vertexs);
	return 0;
}