三、阅读程序

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#include <iostream>
using namespace std;
int main()
{
    int len,maxlen;
    string s,ss;
    maxlen=0;
    do
    {
        cin>>ss;
        len=ss.length();
        if(ss[0]=='#')break;
        if(len>maxlen)
        {
            s=ss;
            maxlen=len;
        }
    }while(true);
    cout<<s<<endl;
    return 0;
}

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#include <iostream>
using namespace std;

int fun(int n,int fromPos,int toPos)
{
    int t,tot;
    if(n==0)return 0;
    for(t=1;t<=3;t++)
        if(t!=fromPos && t != toPos)break;
    tot=0;
    tot+=fun(n-1,fromPos,t);
    tot++;
    tot+=fun(n-1,t,toPos);
    return tot;
}
int main()
{
    int n;
    cin>>n;
    cout<<fun(n,1,3)<<endl;
    return 0;
}