邻接表

图的常用储存结构之一。邻接表由表头结点和表结点两部分组成，其中图中每个顶点均对应一个存储在数组中的表头结点。

http://baike.baidu.com/link?url=356SEBUQpBZT2E2M0Hssd5benLxbyMWd13ZF-DbZi-mvyQEoyssk4eBweeTpfIqZdLN9-g9cTwwqpPVC1WiM5K

除了克鲁斯卡尔和floyd，像广搜，普里姆，Bellman-Ford，迪杰斯特拉，SPFA，拓扑排序等等，都可以用到图的邻接表形式。

数据结构书上的邻接表是这样的：

借用一下这张图

http://blog.csdn.net/linxinyuluo/article/details/6847851

#include <iostream>
using namespace std;

#define MaxVertexNum 20

typedef char VertexType;

typedef struct node
{
          int adjvex;
          node* next;
}EdgeNode;

typedef struct
{
          VertexType data;
          EdgeNode* firstedge;
}VertexNode,AdjList[MaxVertexNum];

typedef struct
{
          AdjList adjlist;
          int n,e;
}ALGraph;

void CreateG(ALGraph *G)
{
          cout<<"Input vex and edge
";
          cin>>G->n>>G->e;
          EdgeNode *p;

          //建立顶点表
          for(int i = 0;i<G->n;i++)
          {
                    cout<<"create vex table "<<i<<endl;
                    cin>>G->adjlist[i].data;
                    G->adjlist[i].firstedge = NULL;
          }

          //建立边表
          for(int k = 0;k<G->e;k++)
          {
                    cout<<"create edge table "<<k<<endl;
                    int a,b;
                    cin>>a>>b;
                    p = new EdgeNode;
                    p->adjvex = b;
                    p->next = G->adjlist[a].firstedge;
                    G->adjlist[a].firstedge  = p;
                    p = new EdgeNode;
                    p->adjvex = a;
                    p->next = G->adjlist[b].firstedge;
                    G->adjlist[b].firstedge  = p;
          }
}

int main()
{
          ALGraph *G = new ALGraph;
          CreateG(G);
          for(int i = 0;i<G->n;i++)
          {
                    cout<<i;
                    while(G->adjlist[i].firstedge!=NULL)
                    {
                              cout<<" -> "<<G->adjlist[i].firstedge->adjvex;
                              G->adjlist[i].firstedge = G->adjlist[i].firstedge->next;
                    }
                    cout<<endl;
          }
}

http://www.cnblogs.com/g0feng/archive/2012/09/18/2690913.html

数组实现：

http://bbs.ahalei.com/thread-4612-1-1.html

思路是先用e[i]保存所有的边，再用pre[i]保存i最后一个边的位置，最后用e[i].next实现跳转

#include <iostream>
using namespace std;

#define MaxVertexNum 20

typedef char VertexType;

typedef struct
{
          int to;
          int w;
          int next;
}Edge;

Edge e[MaxVertexNum];
int pre[MaxVertexNum];

void CreateG(int n,int ed)
{
          for(int i = 1;i<=n;i++)
                    pre[i] = -1;
          for(int i = 1;i<=ed;i++)
          {
                    int from,to,wg;
                    cin>>from>>to>>wg;
                    e[i].to = to;
                    e[i].w = wg;
                    e[i].next = pre[from];
                    pre[from] = i;
          }
}

int main()
{
          cout<<"Input vex and edge
";
          int n,ed;
          cin>>n>>ed;
          CreateG(n,ed);
          /*now为弧尾结点序号，i为now所发出的边序号，adj为弧头结点序号，w为now-->adj这条边的权值*/
          for(int i = 1;i<=n;i++)
          {
                    for(int j = pre[i]; j != -1; j = e[j].next)
                    {
                              int adj = e[j].to;
                              int w = e[j].w;
                              cout<<adj<<" -> "<<i<<" weight: "<<w<<endl;
                    }
          }
          return 0;
}
/*
4 5
1 4 9
4 3 8
1 2 5
2 4 6
1 3 7
*/