题解 | #玛雅人的密码#

#include<iostream>
#include<queue>
#include<string>

using namespace std;

struct mitery{
    int index;
    string s;
    mitery(int i,string ss):index(i),s(ss){}
};

void bfs(string s){
    queue<mitery> q;
    q.push(mitery(0,s));
    while(!q.empty()){
        mitery t=q.front();
        q.pop();
        string ts=t.s;
        if(ts.find("2012")!=string::npos){
            cout<<t.index<<endl;return ;
        }
        for(int i=0;i<ts.size()-1;i++){
            swap(ts[i],ts[i+1]);
            q.push(mitery(t.index+1,ts));
            swap(ts[i],ts[i+1]);
        }
    }
    cout<<-1<<endl;
}
int main(){
    int n;
    string s;
    while(cin>>n>>s){
        bfs(s);
    }
    return 0;
}