manacher马拉车

 1 #include<iostream>
 2 #include<algorithm>
 3 #include<cstring>
 4 using namespace std;
 5 
 6 char ss[110005],s[220010];
 7 int p[220010];
 8 
 9 int init()
10 {
11     s[0]='$'; s[1]='#';
12     int g=2;
13     for(int i=0;ss[i]!='';i++)
14     {
15         s[g++]=ss[i];
16         s[g++]='#';
17     }
18     s[g]='';
19     return g; //·µ»Ø³¤¶È
20 }
21 int manacher()
22 {
23     int len =init();
24     int maxlen =-1;
25 
26     int id;
27     int mx= 0;
28 
29     for(int i=1;i<len;i++)
30     {
31         if(i<mx) p[i]=min( p[2*id-i], mx-i);
32         else p[i]=1;
33 
34         while(s[i-p[i]] == s[i+p[i]] )
35             p[i]++;
36 
37         if(i+p[i] > mx)
38         {
39             id=i;
40             mx=p[i]+i;
41         }
42         maxlen=max(maxlen,p[i]-1);
43     }
44     return maxlen;
45 
46 }
47 
48 int main()
49 {
50     ios::sync_with_stdio(false);
51     while(cin>>ss)
52     {
53         int res=manacher();
54         cout<<res<<endl;
55     }
56 }