**鄰接表對於無向圖的理解

上次我們寫了鄰接矩陣對於無向圖的理解，這次我們繼續，完善鄰接表對於無向圖的代碼。

鄰接表中有兩種結點結構：1.頂點表結點  2.邊表的結點

 

 

頂點表：

vertex：存儲圖中個頂點元素的信息;

fisrtedge：指針域  存儲首個邊表的結點

 

邊表：

adjvex: 鄰接點 頂點表中元素的下標;

next: 指針域  下一個鄰接點

 

無向圖：                                                                                                                                  相對應的鄰接表：

                                               

#include<iostream>
#include<string>
#define maxSize 10
using namespace std;
//定義邊表
struct arcNode {
    int arcNum;  //存儲頂點的下標
    arcNode* next;
};

//定義頂點表
struct verNode {
    string vertex;
    arcNode* firstedg;
};

class ALGraph {
public:
    ALGraph();
    ALGraph(string str[], int verNum, int arcNum);
    ~ALGraph();
    void DFStra(int v);
    void BFStra(int v);
private:
    int verNum;
    int arcNum;
    //存放頂點表的數組
    verNode adjlist[maxSize];
    //頂點是否唄訪問過
    int visited[maxSize] = { 0 };
};

ALGraph::ALGraph() {
    cout << "默認構造函數!" << endl;
}
ALGraph::ALGraph(string str[], int verNum, int arcNum) {
    //圖中頂點的賦值
    this->verNum = verNum;
    for (int i = 0; i < this->verNum; i++) {
        adjlist[i].vertex = str[i];
        adjlist[i].firstedg = NULL;
    }
    this->arcNum = arcNum;
    for (int k = 0; k < this->arcNum; k++) {
        int i = 0;
        int j = 0;
        cout << "請輸入邊依附的頂點下標序號: ";
        cin >> i >> j;
        //單鏈表頭插法  頂點表與邊是雙向的 即鄰接矩陣的數組 arc[i][j]==arc[j][i];
        arcNode* s = new arcNode;
        s->arcNum = j;
        s->next = adjlist[i].firstedg;
        adjlist[i].firstedg= s;

        arcNode* p = new arcNode;
        p->arcNum = i;
        p->next = adjlist[j].firstedg;
        adjlist[j].firstedg = p;
    }
}
ALGraph::~ALGraph() {
    for (int i = 0; i < verNum; i++) {    
        if (adjlist[i].firstedg != NULL) {
            arcNode* p = adjlist[i].firstedg;
            adjlist[i].firstedg = adjlist[i].firstedg->next;
            delete p;
            p = NULL;   //上完廁所洗手
        }
     }
}
void ALGraph::DFStra(int v) {
    cout << adjlist[v].vertex;
    visited[v] = 1;
    arcNode* p = adjlist[v].firstedg;
    while (p != NULL) {
        if (visited[p->arcNum] == 0)
            DFStra(p->arcNum);
        p = p->next;
    }
}
void ALGraph::BFStra(int v) {
    //定義棧並初始化
    int Queue[maxSize];
    int front = -1;
    int rear = -1;
    cout << adjlist[v].vertex;
    visited[v] = 1;
    Queue[++rear] = v;
    while (front != rear) {
        v = Queue[++front];
        arcNode* p = adjlist[v].firstedg;
        //廣度
        while (p != NULL) {
            if (visited[p->arcNum] == 0){
                cout << adjlist[p->arcNum].vertex;
                visited[p->arcNum] = 1;
                Queue[++rear] = p->arcNum;
            }
            p = p->next;
        }
    }
}

int main() {
    string str[4] = { "v0","v1","v2","v3" };
    ALGraph myALGraph(str,4,4);
    //myALGraph.DFStra(1);
    //myALGraph.BFStra(1);
    return 0;
}