题解 | #密码锁#（深度必超时 玛雅人不超时因为字符串短）

#include<iostream>
#include<vector>
#include<string>
#include<algorithm>
#include<queue>
#include<map>
using namespace std;
struct ele                //记录层数
{
	string str;
	int step;
};
int BFS(string s)                  //广度搜索
{
	map<string, int> visited;        //访问标记数组
	queue<ele> con;            //保存数据队列
	ele k;
	k.str = s;
	k.step = 0;
	con.push(k);
	visited[s] = 1;
	int step = -1;

	while (!con.empty())
	{
		
	    ele z = con.front();
        con.pop();
		if (z.str.find("2012") != string::npos)
		{
			step = z.step;
			break;
		}
		else
		{
			z.step++;
			for (int i = 0; i < z.str.size() - 1; i++)
			{
				swap(z.str[i], z.str[i + 1]);
				if (visited.find(z.str) == visited.end())
				{
					con.push(z);
					visited[z.str] = 1;
				}
				swap(z.str[i], z.str[i + 1]);
			}
		}
	}
	return step;

}
int main()
{
	int n;
	while (cin >> n)
	{
		string s;
		cin >> s;
		cout << BFS(s) << endl;
	
	
	}

}