图的广度优先遍历

#include<iostream>
using namespace std;

int main() {
	int i, j, n, m, e[101][101], book[101] = { 0 },a,b,cur;
	int que[10001], head, tail;
	cin >> n >> m;
	for (i = 1;i <= n;i++)
		for (j = 1;j <= n;j++)
			if (i == j)
				e[i][j] = 0;
			else
				e[i][j] = -1;
	for (i = 1;i <= m;i++)
	{
		cin >> a >> b;
		e[a][b] = 1;
		e[b][a] = 1;
	}
	//初始化
	head = 1;
	tail = 1;
	que[tail] = 1;
	tail++;
	book[1] = 1;
	while (head < tail) {
		cur = que[head];//当前正在访问的顶点编号
		for (i = 1;i <= n;i++) {
			if (e[cur][i] == 1 && book[i] == 0) {
				que[tail] = i;
				book[i] = 1;
				tail++;
			}
			//如果tail大于n，表明所有顶点都已经被访问过
			if (tail > n) {
				break;
			}
		}
		head++;
	}
	for (i = 1;i < tail;i++)
		cout << que[i]<<" ";

	return 0;
}