Problem Description

One day, sailormoon girls are so delighted that they intend to research about palindromic strings. Operation contains two steps:

First step: girls will write a long string (only contains lower case) on the paper. For example, "abcde", but ‘a‘ inside is not the real ‘a‘, that means if we define the ‘b‘ is the real ‘a‘, then we can infer that ‘c‘ is the real ‘b‘, ‘d‘ is the real ‘c‘ ……, ‘a‘ is the real ‘z‘. According to this, string "abcde" changes to "bcdef".
Second step: girls will find out the longest palindromic string in the given string, the length of palindromic string must be equal or more than 2.

Input

#include<cstdio>
#include<cstring>
#include<iostream>
const int maxn=400010;
using namespace std;
char c[2],s[maxn];
int pos,len,p[maxn],a;
int main()
{
    while(~scanf("%s %s",c,s))
    {
        len=strlen(s);pos=0;a=0;
        for(int i=len;i>=0;i--)
        {
            s[i*2+2]=s[i];
            s[i*2+1]=‘#‘;
        }
        s[0]=‘&‘;p[0]=0;
        for(int i=2;i<len*2+1;i++)
        {
            if(pos+p[pos]>i)p[i]=min(p[pos*2-i],pos+p[pos]-i);
            else p[i]=1;
            while(s[i+p[i]]==s[i-p[i]])p[i]++;
            if(pos+p[pos]<i+p[i])pos=i;
            if(p[a]<p[i])a=i;
        }
        if(p[a]-1<2)printf("No solution!\n");
        else{
            printf("%d %d\n",(a-p[a]+2)/2-1,(a+p[a]-2)/2-1);
            int k=c[0]-‘a‘;
            for(int i=a-p[a]+2;i<=a+p[a]-2;i+=2)printf("%c",(s[i]-‘a‘-k+26)%26+‘a‘);
            printf("\n");
        }
    }
    return 0;
}

【hdu3294】Girls' research——manacher