本身就是一個簡單的深搜列舉問題，這裡主要是提醒自己關於遞迴函式關於遞迴次數的理解

自己腦抽了一直沒注意到這個問題，連樣例都沒過。最後發現問題。

程式碼：

#include<iostream>
#include<cstdio>
#include<stack>
#include<vector>
#include<cstdlib>
#include<cstring>

using namespace std;

vector<int>vec[20];
int vis[30], path[30];
int kase = 0;
 
void dfs(int x, int tar, int cnt)
{
		if (x == tar && cnt == 20)
		{
				printf("%d:  ", ++kase);
				stack<int>iron;
				iron.push(x);
				while (path[x] != -1)
				{
						iron.push(path[x]);
						x = path[x];
						if (x == tar)		break;
				}
				while (iron.size()!=1)
				{
						int t = iron.top();
						iron.pop();
						printf("%d ", t);
				}
				printf("%d", iron.top());
				printf("\n");
				return;
		}
		for (int i = 0; i < vec[x].size(); i++)
		{
				int t = vec[x][i];
				if (t == x)		continue;
				if (vis[t])		continue;
				if (t == tar && cnt != 19)		continue;
				path[t] = x;
				vis[t] = 1;
				dfs(t, tar, cnt + 1);
				path[t] = -1;
				vis[t] = 0;
		}
}

void ini()
{
		memset(vis, 0, sizeof(vis));
		memset(path, -1, sizeof(path));
}

int main()
{
		for (int i = 1; i <= 20; i++)
		{
				int a, b, c;
				scanf("%d %d %d", &a, &b, &c);
				vec[i].push_back(a);
				vec[i].push_back(b);
				vec[i].push_back(c);
		}	
		int m;
		//scanf("%d", &m);
		ini();
		while (scanf("%d", &m) && m != 0)
		{
				for (int i = 0; i < vec[m].size(); i++)
				{
						int t = vec[m][i];
						vis[t] = 1;
						path[t] = m;
						dfs(t, m, 1);
						vis[t] = 0;
						path[t] = -1;
				}
		}
		//system("pause");
		return 0;
}