HDU 3068 最长回文

Posted 2020-06-18 blues

最长回文串模板题

Manacher 算法

 1 #include<cstdio>
 2 #include<cstring>
 3 #include<algorithm>
 4 #include<iostream>
 5 #include<cstdlib>
 6 #include<string>
 7 #include<cmath>
 8 #include<vector>
 9 using namespace std;
10 const int maxn=1e5+7;
11 const double eps=1e-8;
12 const double pi=acos(-1);
13 #define ll long long
14 #define clc(a,b) memset(a,b,sizeof(a))
15 
16 int Proc(char pszIn[],char pszOut[])
17 {
18     int nLen=1;
19     pszOut[0]=‘$‘;
20     int i=0;
21     while(pszIn[i]!=‘\0‘)
22     {
23         pszOut[nLen++]=‘#‘;
24         pszOut[nLen++]=pszIn[i];
25         i++;
26     }
27     pszOut[nLen++]=‘#‘;
28     pszOut[nLen]=0;
29     return nLen;
30 }
31 void Manacher(int *p,char *str,int len)
32 {
33     int mx=0,id=0;
34     for(int i=0; i<len; i++)
35     {
36         p[i]=mx>i?min(p[2*id-i],mx-i):1;
37         while(str[i+p[i]]==str[i-p[i]])p[i]++;
38         if(i+p[i]>mx)
39         {
40             mx=i+p[i];
41             id=i;
42         }
43     }
44 }
45 const int MAXN=220010;
46 char strIn[MAXN];
47 char strOut[MAXN];
48 int p[MAXN];
49 int main()
50 {
51     while(scanf("%s",strIn)!=EOF)
52     {
53         int nLen=Proc(strIn,strOut);
54         Manacher(p,strOut,nLen);
55         int ans=1;
56         for(int i=0; i<nLen; i++)
57             ans=max(ans,p[i]);
58         printf("%d\n",ans-1);
59     }
60     return 0;
61 }

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