BFS（邻接矩阵表示）

#define _CRT_SECURE_NO_WARNINGS
#include <iostream>
#include <queue>
using namespace std;

#define VERTEX_NUM 8

bool visited[VERTEX_NUM + 1];            // 访问标志数组（备忘表）

int FirstAdjVex(bool G[VERTEX_NUM + 1][VERTEX_NUM + 1], int v)
{
    for (int j = 1; j <= VERTEX_NUM; j++) {
        if (G[v][j] == 1)
            return j;
    }
    cout << "该点是孤立点" << endl;        // 连通图则不会到这一步
    return -1;
}

int NextAdjVex(bool G[VERTEX_NUM + 1][VERTEX_NUM + 1], int v, int w)
{
    for (int j = w + 1; j <= VERTEX_NUM; j++) {
        if (G[v][j] == 1)
            return j;
    }
    return -1;
}

void BFSTraverse(bool G[VERTEX_NUM + 1][VERTEX_NUM + 1])
{
    // 按广度优先非递归遍历图G。使用辅助队列Q和访问标志数组visited。
    int v;
    int w;
    queue<int> Q;
    int u;
    for (v = 1; v <= VERTEX_NUM; ++v)
        visited[v] = false;
    for (v = 1; v <= VERTEX_NUM; ++v) {
        if (!visited[v]) {                    // v尚未访问
            visited[v] = true;
            cout << v << endl;
            Q.push(v);
            while (!Q.empty()) {
                u = Q.front();
                Q.pop();                    // 队头元素出队并置为u
                for (w = FirstAdjVex(G, u); w >= 0; w = NextAdjVex(G, u, w)) {
                    if (!visited[w]) {        // u的尚未访问的邻接顶点w入队列Q
                        visited[w] = true;
                        cout << w << endl;
                        Q.push(w);
                    }
                }
            }
        }
    }
}

void CreatAdjMatrixGraph(bool G[VERTEX_NUM + 1][VERTEX_NUM + 1])
{
    int a;
    int b;
    while (cin >> a >> b, !(a == 0 && b == 0)) {    //以0 0作为输入结束
        G[a][b] = 1;
        G[b][a] = 1;
    }
}

void Display(bool G[VERTEX_NUM + 1][VERTEX_NUM + 1])
{
    for (int i = 1; i <= VERTEX_NUM; i++) {            // 输出邻接矩阵
        for (int j = 1; j <= VERTEX_NUM; j++) {
            cout << G[i][j] << ' ';
        }
        cout << endl;
    }
}

int main(int argc, char **argv)
{
    freopen("cin.txt", "r", stdin);
    bool G[VERTEX_NUM + 1][VERTEX_NUM + 1] = {0};

    CreatAdjMatrixGraph(G);

    Display(G);

    BFSTraverse(G);

    return 0;
}

/* cin.txt:
1 2
2 4
2 5
8 4
8 5
1 3
3 6
3 7
6 7
0 0
*/

运行结果：