图由点和线组成
知道了图中有多少个点，和哪些点之间有线，就可以把一张图描绘出来
点之间的线，分有方向和无方向
创建图创建图，实际就是创建出节点，和节点之间的线。
下面的代码实现了上面的图的创建
graph_link.h
#ifndef __graph_link__
#define __graph_link__
#include <stdio.h>
#include <malloc.h>
#include <assert.h>
#include <memory.h>
#define default_vertex_size 10
#define T char
//边的结构
typedef struct Edge{
//顶点的下标
int idx;
//指向下一个边的指针
struct Edge* link;
}Edge;
//顶点的结构
typedef struct Vertex{
//顶点的值
T data;
//边
Edge* adj;
}Vertex;
//图的结构
typedef struct GraphLink{
int MaxVertices;
int NumVertices;
int NumEdges;
Vertex* nodeTable;
}GraphLink;
//初始化图
void init_graph_link(GraphLink* g);
//显示图
void show_graph_link(GraphLink* g);
//插入顶点
void insert_vertex(GraphLink* g, T v);
//插入边尾插
void insert_edge_tail(GraphLink* g, T v1, T v2);
//插入边头插
void insert_edge_head(GraphLink* g, T v1, T v2);
//删除边
void remove_edge(GraphLink* g, T v1, T v2);
//删除顶点
void remove_vertex(GraphLink* g, T v);
//销毁图
void destroy_graph_link(GraphLink* g);
//取得指定顶点的第一个后序顶点
int get_first_neighbor(GraphLink* g, T v);
//取得指定顶点v1的临街顶点v2的第一个后序顶点
int get_next_neighbor(GraphLink* g, T v1, T v2);
#endif
graph_link.c
#include "graph_link.h"
//初始化图
void init_graph_link(GraphLink* g){
g->MaxVertices = default_vertex_size;
g->NumVertices = g->NumEdges = 0;
g->nodeTable = (Vertex*)malloc(sizeof(Vertex) * g->MaxVertices);
assert(NULL != g->nodeTable);
for(int i = 0; i < g->MaxVertices; ++i){
g->nodeTable[i].adj = NULL;
}
}
//显示图
void show_graph_link(GraphLink* g){
if(NULL == g)return;
for(int i = 0; i < g->NumVertices; ++i){
printf("%d %c->", i, g->nodeTable[i].data);
Edge* p = g->nodeTable[i].adj;
while(NULL != p){
printf("%d->", p->idx);
p = p->link;
}
printf(" NULL\n");
}
}
//插入顶点
void insert_vertex(GraphLink* g, T v){
if(g->NumVertices >= g->MaxVertices)return;
g->nodeTable[g->NumVertices++].data = v;
}
//查找顶点的index
int getVertexIndex(GraphLink* g, T v){
for(int i = 0; i < g->NumVertices; ++i){
if(v == g->nodeTable[i].data)return i;
}
return -1;
}
//创建边
void buyEdge(Edge** e, int idx){
Edge* p = (Edge*)malloc(sizeof(Edge));
p->idx = idx;
p->link = NULL;
if(NULL == *e){
*e = p;
}
else{
Edge* tmp = *e;
while(tmp->link != NULL){
tmp = tmp->link;
}
tmp->link = p;
}
}
//插入边(尾插）
void insert_edge_tail(GraphLink* g, T v1, T v2){
int p1 = getVertexIndex(g, v1);
int p2 = getVertexIndex(g, v2);
if(p1 == -1 || p2 == -1)return;
buyEdge(&(g->nodeTable[p1].adj), p2);
g->NumEdges++;
buyEdge(&(g->nodeTable[p2].adj), p1);
g->NumEdges++;
}
//插入边(头插）
void insert_edge_head(GraphLink* g, T v1, T v2){
int p1 = getVertexIndex(g, v1);
int p2 = getVertexIndex(g, v2);
if(p1 == -1 || p2 == -1)return;
Edge* p = (Edge*)malloc(sizeof(Edge));
p->idx = p2;
p->link = g->nodeTable[p1].adj;
g->nodeTable[p1].adj = p;
p = (Edge*)malloc(sizeof(Edge));
p->idx = p1;
p->link = g->nodeTable[p2].adj;
g->nodeTable[p2].adj = p;
}
//删除边
int remove_edge_(Edge** p, int i){
if(NULL == *p)return -1;
Edge* f;
//判断第一个边是否是目标边
if((*p)->idx == i){
//删除第一条边
f = *p;
*p = (*p)->link;
free(f);
return 0;
}