回文(manacher)

裸manacher

我竟然写跪了…………

一个地方（偶数）没写清楚……

我OOXOXOXOXXOXO

 

#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<iostream>
#include<algorithm>
#include<functional>
#include<cmath>
#include<cctype>
#include<cassert>
#include<climits>
using namespace std;
#define For(i,n) for(int i=1;i<=n;i++)
#define Rep(i,n) for(int i=0;i<n;i++)
#define Fork(i,k,n) for(int i=k;i<=n;i++)
#define ForD(i,n) for(int i=n;i;i--)
#define Forp(x) for(int p=pre[x];p;p=next[p])
#define RepD(i,n) for(int i=n;i>=0;i--)
#define MEM(a) memset(a,0,sizeof(a))
#define MEMI(a) memset(a,127,sizeof(a))
#define MEMi(a) memset(a,128,sizeof(a))
#define INF (2139062143)
#define F (1000000009)
#define MAXN (16777216+10)
typedef long long ll;
int n,r[MAXN],maxlen,maxbegin;
char s[MAXN];
int main()
{
   freopen("palindrome.in","r",stdin);
   freopen("palindrome.out","w",stdout);
   
   scanf("%s",s+1);n=strlen(s+1);
   int j=0;r[0]=0;
   For(i,n)
   {
      r[i]=1;
      if (j+r[j]>i) r[i]=min(r[j-(i-j)],j+r[j]-i);
      while (i-r[i]>=1&&i+r[i]<=n&&s[i-r[i]]==s[i+r[i]]) r[i]++;       
      if (i+r[i]>j+r[j]) j=i;
   }
   maxlen=0;
   For(i,n) if (maxlen<r[i]*2-1) maxlen=r[i]*2-1,maxbegin=i-r[i]+1;
// cout<<maxlen<<' '<<maxbegin<<endl;   
// For(i,n) cout<<r[i]<<' ';
   
   j=0;r[0]=0;memset(r,0,sizeof(r));
   For(i,n-1)
   {
      r[i]=0;
      if (j+r[j]>i) r[i]=min(r[j-(i-j-1)-1],j+r[j]-i);
      while (i+1-r[i]>1&&i+r[i]<n&&s[i-r[i]]==s[i+1+r[i]]) r[i]++;       
      if (i+r[i]>j+r[j]) j=i;
   }
   For(i,n-1) if (maxlen<r[i]*2) maxlen=r[i]*2,maxbegin=i-r[i]+1;
   
   printf("%d\n",maxlen);
   Fork(i,maxbegin,maxbegin+maxlen-1) putchar(s[i]);puts("");
   
//   cout<<maxlen<<' '<<maxbegin<<endl;   
   
   
// while(1);
   return 0;
}