https://blog.csdn.net/libin56842/article/details/15028427

#include<bits/stdc++.h>
using namespace std;
int mp[25][5];
bool VIS[25];
int ans[25];
int T = 1;
int n, m;
void DFS(int u, int cnt)
{
	VIS[u] = 1;
	ans[cnt] = u;
	for (int i = 0; i<3; i++)
	{
		int v = mp[u][i];
		if (v == m && cnt == 19)
		{
			printf("%d:  ", T++);
			for (int j = 0; j < 20; j++)
				cout << ans[j] << " ";
			cout << m << endl;
		}
		if (!VIS[v]) DFS(v, cnt + 1);
	}
	VIS[u] = 0;
}
int main()
{
	for (int i = 1; i <= 20; i++) 
	{
		cin >> mp[i][0] >> mp[i][1] >> mp[i][2];
		sort(mp[i], mp[i] + 3);
		//如有多條路線,按字典序輸出
	}

	while (cin>>m&&m)
	{
		memset(VIS, 0, sizeof(VIS));
		DFS(m, 0);
	}
	return 0;
}