C语言邻接表建立图详解

#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<stack>
using namespace std;
#define maxn 200
int v, e;
//表结点
typedef struct _Enode
{
	int ivex; //该边所指向的节点位置
	int value;//如果边有权值的话，就对其赋值
	struct _Enode* next_edge; //指向下一条边
}ENode,*PENode;
//头结点
typedef struct _VNode
{
	int data;
	ENode* fidt_edge;
}VNode;

//邻接表
typedef struct _LGraph
{
	int vex_num; //点的数量
	int edg_num; //边的数量
	VNode vexs[maxn]; //一维数组存表头节点
}LGraph;

LGraph* create()
{
	LGraph* pG;
	pG = (LGraph*)malloc(sizeof(LGraph));
	memset(pG, 0, sizeof(LGraph));
	pG->vex_num = v;  //顶点数
	pG->edg_num = e; //边数
	for (int i = 0; i < v; ++i) //初始化定点表的指针域为空
		pG->vexs[i].fidt_edge = NULL;
	//建立链表
	for (int i = 0; i < e; ++i) 
	{
		int v1, v2;
		scanf_s("%d%d", &v1, &v2);
		ENode* p1 = (ENode*)malloc(sizeof(ENode));  //为新建的边申请空间
		p1->ivex = v2;//该边指向的节点
		// 头插法建立
		p1->next_edge = pG->vexs[v1].fidt_edge;
		pG->vexs[v1].fidt_edge = p1;
	}
	return pG;
}
int main()
{
	while (~scanf_s("%d%d", &v, &e))
	{
		if (v == 0 && e == 0)
			break;
		LGraph* pG;
		pG = create();
	}
	return 0;
}

//建立链表
	for (int i = 0; i < e; ++i) 
	{
		int v1, v2;
		scanf_s("%d%d", &v1, &v2);
		ENode* p1 = (ENode*)malloc(sizeof(ENode));  //为新建的边申请空间
		p1->ivex = v2;//该边指向的节点
		// 头插法建立
		p1->next_edge = pG->vexs[v1].fidt_edge;
		pG->vexs[v1].fidt_edge = p1;
		//另一条边
		ENode* p2 = (ENode*)malloc(sizeof(ENode));  //为新建的边申请空间
		p2->ivex = v1;//该边指向的节点
		// 头插法建立
		p2->next_edge = pG->vexs[v2].fidt_edge;
		pG->vexs[v2].fidt_edge = p2;
	}

#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<stack>
using namespace std;
#define maxn 200
int v, e;
//表结点
typedef struct _Enode
{
	int ivex; //该边所指向的节点位置
	struct _Enode* next_edge; //指向下一条边
}ENode,*PENode;
//头结点
typedef struct _VNode
{
	int data;
	int indegree;//记录定点的入度
	ENode* fidt_edge;
}VNode;

//邻接表
typedef struct _LGraph
{
	int vex_num; //点的数量
	int edg_num; //边的数量
	VNode vexs[maxn]; //一维数组存表头节点
}LGraph;

LGraph* create()
{
	LGraph* pG;
	pG = (LGraph*)malloc(sizeof(LGraph));
	memset(pG, 0, sizeof(LGraph));
	pG->vex_num = v;  //顶点数
	pG->edg_num = e; //边数
	for (int i = 0; i < v; ++i) //初始化定点表的指针域为空
		pG->vexs[i].fidt_edge = NULL;
	for (int i = 0; i < e; ++i)
	{
		int v1, v2;
		scanf_s("%d%d", &v1, &v2);
		ENode* p1 = (ENode*)malloc(sizeof(ENode));  //为新建的边申请空间
		p1->ivex = v2;//该边指向的节点
		// 头插法建立
		p1->next_edge = pG->vexs[v1].fidt_edge;
		pG->vexs[v1].fidt_edge = p1;
	}
	return pG;
}
void TopSort(LGraph* pG)
{
	stack<int>s;
	int count, k, i;
	ENode* p;
	for (int i = 0; i < v; ++i) //记录各个顶点的入度
	{
		//遍历整个邻接表，如果表结点的值为 i，则i对应的头结点的入度加1
		p = pG->vexs[i].fidt_edge; //获得其指向的第一条边
		while (p)
		{
			pG->vexs[p->ivex].indegree++; //该边表存的位置对应的头结点的入度数量加1
			p = p->next_edge;
		}
	}
	//将入度为0的压入栈中
	for (int i = 0; i < v; ++i)
		if (pG->vexs[i].indegree == 0)s.push(i);
	count = 0;//对输出的顶点计数
	while (!s.empty())
	{
		int k = s.top(); //取出
		s.pop();
		++count;
		//与k节点相邻的节点的入度减1
		for (p = pG->vexs[k].fidt_edge; p; p = p->next_edge)
		{
			int to;
			to = p->ivex;
			pG->vexs[to].indegree--;
			//减为0的话就压入栈中
			if (pG->vexs[to].indegree == 0)
				s.push(to);
		}
	}
	if (count < pG->vex_num)
		printf("NO\n");
	else
		printf("YES\n");
}
int main()
{
	while (~scanf_s("%d%d", &v, &e))
	{
		if (v == 0 && e == 0)
			break;
		LGraph* pG;
		pG = create();
		TopSort(pG);
	}
	return 0;
}