构造图采用的是邻接表的方法，然后采用深度和广度优先进行遍历。（博主第一次写构造方法的时候花了很久写的很冗杂，虽然也实现了，但是感觉到处都在打补丁，拼拼凑凑写出来的，后来用了一分钟重写了一个，秒通过！！！欲哭无泪啊~原因主要是因为不同的输入格式导致的，以后些其他代码的时候要慎重考虑输入的格式问题）

下面贴代码！

根据书上的伪代码，写出定义的结构

const int MAX_VERTEX_NUM = 20;
bool visited[MAX_VERTEX_NUM];    //遍历访问标志

typedef struct ArcNode{
    int adjvex;    //该弧所指向的顶点的位置
    struct ArcNode *nextarc;    //指向下一条弧（边）的指针
    int weight;    //该弧（边）的权值
}ArcNode;

typedef struct VNode{
    char data;    //顶点信息
    ArcNode *firstarc;    //指向第一条依附该顶点的弧（边）的指针
}VNode,AdjList[MAX_VERTEX_NUM];

typedef struct{
    AdjList vertices;    
    int vexnum, arcnum;    //图的当前顶点数和弧（边）数
    int kind;
}ALGraph;

根据书上的伪代码，写出三个要用到的方法

//返回顶点v在图G中的位置
int LocateVex(ALGraph G, char v)
{
    for (int i = 0; i < G.vexnum; i++){
        if (v == G.vertices[i].data)
            return i;
    }
    return -1;
}

//返回v的第一个邻接顶点
int FirstAdjVex(ALGraph G, int v)
{
    if (G.vertices[v].firstarc)
        return G.vertices[v].firstarc->adjvex;
    return -1;
}

//返回顶点v相对于邻接点w的下一个邻接点
int NextAdjVex(ALGraph G, int v, int w)
{
    ArcNode *p;
    p = G.vertices[v].firstarc;
    if (p){
        while (p){
            if (w == p->adjvex){
                if (nullptr == p->nextarc)
                    return -1;
                else
                    return p->nextarc->adjvex;
            }
            p = p->nextarc;
        }
    }
    return -1;
}

下面是本体，一分钟改写出的构造图的方法！

//采用邻接表构造图G
void CreateGraph(ALGraph &G)
{
    int i, j, weight;
    char v, v1, v2;
    ArcNode *p, *q = nullptr;
    cout << "请输入图类型的序号：\n1.DG(有向图)\n2.DN(有向网\n3.UDG(无向图)\n4.UDN(无向网)" << endl;
    cin >> G.kind;
    cout << "请输入图G的顶点数和弧（边）数：";
    cin >> G.vexnum >> G.arcnum;
    //构造邻接表
    for (i = 0; i < G.vexnum; i++){
        cout << "请输入顶点vex[" << i << "]的值：";
        cin >> G.vertices[i].data;
        G.vertices[i].firstarc = nullptr;
    }
    cout << endl;
    for (j = 0; j < G.arcnum; j++){
        cout << "请输入第" << j << "条弧（边）的两个端点：";
        cin >> v1 >> v2;
        q = G.vertices[LocateVex(G, v1)].firstarc;
        p = new ArcNode;
        p->adjvex = LocateVex(G, v2);
        p->nextarc = nullptr;
        if (1 == G.kind || 3 == G.kind)
            p->weight = 1;
        else{
            cout << "请输入该弧（边）的权值：";
            cin >> weight;
            p->weight = weight;
        }

        if (q){
            while (q->nextarc)
                q = q->nextarc;
            q->nextarc = p;
        }
        else
            G.vertices[LocateVex(G, v1)].firstarc = p;

        if (3 == G.kind || 4 == G.kind){
            q = G.vertices[LocateVex(G, v2)].firstarc;
            p = new ArcNode;
            p->adjvex = LocateVex(G, v1);
            p->nextarc = nullptr;
            if (1 == G.kind || 3 == G.kind)
                p->weight = 1;
            else{
                p->weight = weight;
            }

            if (q){
                while (q->nextarc)
                    q = q->nextarc;
                q->nextarc = p;
            }
            else
                G.vertices[LocateVex(G, v2)].firstarc = p;
        }
    }
}

根据书上的伪代码，写出深度优先遍历的递归方法

//深度优先遍历（递归）
void DFS(ALGraph G, int v)
{
    visited[v] = true;
    cout << G.vertices[v].data << " ";
    for (int i = FirstAdjVex(G, v); i >= 0; i = NextAdjVex(G, v, i)){
        if (!visited[i])
            DFS(G, i);
    }
}

void DFSTraverse(ALGraph G)
{
    int i;
    cout << "深度优先结果：" << endl;
    for (i = 0; i < G.vexnum; i++)
        visited[i] = false;
    for (i = 0; i < G.vexnum; i++){
        if (!visited[i])
            DFS(G, i);
    }
    cout << endl;
}

打印函数在测试的时候不可少

//打印邻接表
void PrintALGraph(ALGraph G)
{
    ArcNode *p;
    for (int i = 0; i < G.vexnum; i++){
        cout << G.vertices[i].data;
        if (G.vertices[i].firstarc){
            p = G.vertices[i].firstarc;
            while (p){
                if (3 == G.kind || 4 == G.kind)
                    cout << " - " << G.vertices[p->adjvex].data;
                else
                    cout << "→" << G.vertices[p->adjvex].data;
                p = p->nextarc;
            }
        }
        cout << endl;
    }
}

最后配上主函数

int main()
{
    ALGraph graph;
    CreateGraph(graph);
    PrintALGraph(graph);
    DFSTraverse(graph);

    system("pause");
    return 0;
}