bfs广度优先搜索—邻接矩阵 + 邻接表

邻接矩阵

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

const int N = 1e2 + 10;
//n个顶点，m条边
int n, m;
//邻接矩阵
int g[N][N];
//标记数组
bool vis[N];//vis[2]=1/0  代表2号点   1-被标记  0-没被标记
void bfs(int s/*搜索的起点*/) {
	queue<int>q;
	q.push(s);
	vis[s] = 1;
	while (!q.empty()) {
		int v = q.front();
		q.pop();
		cout << v << " ";
		for (int i = 1; i <= n; i++) {
			if (!vis[i] && g[v][i] == 1) {
				q.push(i);
				vis[i] = 1;
			}
		}
	}
}

int main() {

	cin >> n >> m;

	for (int i = 1; i <= m; i++) {
		int u, v; cin >> u >> v;
		g[u][v] = g[v][u] = 1;
	}

	int s; cin >> s;
	bfs(s);//从起点s开始深搜
	return 0;
}

邻接表

#include<iostream>
#include<queue>
#include<vector>
using namespace std;

const int N = 1e4 + 10;
vector<int> g[N];//邻接表存图
bool vis[N];//标记数组-防止重复搜索
int n, m, s;//n-点数  m-边数  s-搜索起点

void bfs(int start/*搜索的起点*/) {
	queue<int> q;
	//1.起点入队+标记
	q.push(start);  vis[start] = 1;

	while (!q.empty()) {

		//2.搜索队首元素，并弹出队列
		int v = q.front();  q.pop();
		cout << v << " ";
		//3.找到v点所有邻接点，入队+标记
		for (auto u: g[v]) {
			if (!vis[u]) {//u是v的邻接点且u没有被搜索过
				q.push(u);  vis[u] = 1;
			}
		}
	}
}

int main() {

	cin >> n >> m;
	for (int i = 1; i <= m; i++) {
		int u, v;  cin >> u >> v;
		g[u].push_back(v);  g[v].push_back(u);
	}
	cin >> s;
	bfs(s);//从起点s开始搜索
	return 0;
}