题解 | #密码截取#

#include<iostream>
#include<string>
using namespace std;

int main()
{
    string str1;
    while(cin>>str1)
    {
        int len1=str1.length();
        string str;
        for(int i=0;i<len1;++i)
        {
            if(isalnum(str1[i]))
                str+=str1[i];
        }
        int len=str.length();
        int index=0;
        int index1=0,index2=0;
        for(int i=0;i<len;++i)
        {
            index1=0;
            index2=1;
            int m=i,n=i+1;
            while(str[m]==str[n]&&n<len&&m>=0)
            {
                index1+=2;
                m--;
                n++;
            }
            int a=i,b=i+2;
            while(str[a]==str[b]&&b<len)
            {
                index2+=2;
                a--;
                b++;
            }
            if(index1>index)    index=index1;
            if(index2>index)    index=index2;
        }
        cout<<index<<endl;
    }
    
    return 0;
}