Manacher || Luogu P3805【模板】manacher算法

 1 #include<cstdio>
 2 #include<cstring>
 3 #include<iostream>
 4 #define max(a,b) ((a)>(b)?(a):(b))
 5 #define min(a,b) ((a)<(b)?(a):(b))
 6 using namespace std;
 7 const int maxn=11000000+50;
 8 int len,N,mr,mid,RL[maxn<<1],ans=1;
 9 char S[maxn<<1],a[maxn];
10 inline void Manacher(){
11     mr=mid=0;
12     for(int i=1;i<=len;i++){
13         if(i<mr) RL[i]=min(RL[(mid<<1)-i],mr-i);
14         else RL[i]=1;
15         while(i-RL[i]>=1&&i+RL[i]<=len&&
16               S[i-RL[i]]==S[i+RL[i]])RL[i]++;
17         if(i+RL[i]-1>mr){
18             mr=i+RL[i]-1;
19             mid=i;
20         }
21         ans=max(ans,RL[i]-1);
22     }
23     return;
24 }
25 int main(){
26     scanf("%s",a);
27     N=strlen(a);
28     S[len=1]=‘#‘;
29     for(int i=0;i<N;i++){
30         S[++len]=a[i];
31         S[++len]=‘#‘;
32     }
33     Manacher();
34     printf("%d\n",ans);
35     return 0;
36 }