C++求字符串最大回文长度

#include<string>
#include<iostream>
#include<algorithm>

using namespace std;

int main()
{
string str，str1，str2，maxstring;


int maxlength =1;

cout<<"请输入一段字符串： "<<endl;

       cin>>str;

    for(int i=0;i<str.size()-1;i++)
{
for( int j=2; j<= str.size()-i; j++)
{
str1 = str.substr(i,j);
str2 = str1;
reverse(str1.begin(),str1.end());
if (str1==str2)
{
if(str2.size()>maxlength)
{
maxlength = str2.size();
maxstring = str2;
}
}
}
}


cout<<maxstring<<endl;
cout<<maxlength<<endl;




return 0;
}