# 图的遍历——BFS（队列实现）

```#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <queue>
#include <malloc.h>

using namespace std;

const int VERTEX_NUM = 20;
const int INFINITY = 0x7fffffff; 		// 最大int型数，表示权的无限值

bool vis[VERTEX_NUM];

class Graph {
public:
int vexNum;
int edgeNum;
int vex[VERTEX_NUM];
int arc[VERTEX_NUM][VERTEX_NUM];
};

void createGraph(Graph &G)
{
cout << "please input vexNum and edgeNum: ";
cin >> G.vexNum >> G.edgeNum;
for (int i = 0; i != G.vexNum; ++i) {
cout << "please input no" << i+1 << " vertex: ";
cin >>  G.vex[i];
}
for (int i = 0; i != G.vexNum; ++i) {
for (int j = 0; j != G.vexNum; ++j) {
G.arc[i][j] = INFINITY;
}
}
for (int k = 0; k != G.edgeNum; ++k) {
cout << "please input the vertex of edge(vi, vj) and weight: ";
int i, j, w;
cin >> i >> j >> w;
G.arc[i][j] = w;
G.arc[j][i] = G.arc[i][j];			// 无向图
}
}

void BFSTraverse(const Graph &G)
{
memset(vis, false, VERTEX_NUM);
queue<int> q;
for (int i = 0; i != G.vexNum; ++i) {
if (!vis[i]) {
vis[i] = true;
cout << G.vex[i] << " ";
q.push(i);
while (!q.empty()) {
int m = q.front();	// 队列的作用正在于此
q.pop();		// ...
for (int j = 0; j != G.vexNum; ++j) {
if (G.arc[m][j] != INFINITY && !vis[j]) {
cout << G.vex[j] << " ";
q.push(j);
vis[j] = true;
}
}
}
}
}
}

int main()
{
Graph G;
createGraph(G);
BFSTraverse(G);
return 0;
}
```

原文作者：GGBeng
原文地址: https://www.cnblogs.com/xzxl/p/8646694.html
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