题解 | #密码截取#
密码截取
http://www.nowcoder.com/practice/3cd4621963e8454594f00199f4536bb1
C++代码，算法效率较高：
#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;
} 
