吉哥系列故事——完美队形II

 1 #include<iostream>
 2 #include<cstdio>
 3 #include<cstring>
 4 #include<algorithm>
 5 #define  M 800050
 6 using namespace std;
 7 int  str1[M],str[M*2];
 8 int rad[M];
 9 void Manacher(int *rad, int  *str,int n){
10   int i,mx=0,id;
11   for(int i=1;i<n;i++){//下标从1开始
12     if(mx>i){
13      rad[i]=min(rad[2*id-i],mx-i);
14     }
15     else rad[i]=1;
16     while(str[i+rad[i]]==str[i-rad[i]]){
17         if(str[i+rad[i]]!=40){
18             if(str[i+rad[i]]<=str[i+rad[i]-2])
19                  rad[i]++;
20             else
21                 break;
22         }
23         else
24             rad[i]++;
25     }
26         if(rad[i]+i>mx){
27             mx=rad[i]+i;
28             id=i;
29         }
30   }
31 }
32 int main(){
33    int ans,cas;
34    scanf("%d",&cas);
35    while(cas--){
36        int nn;
37       scanf("%d",&nn);
38    for(int i=0;i<nn;i++)
39       scanf("%d",&str1[i]);
40      memset(str,0,sizeof(str));
41      int n=nn*2+2;
42      str[0]=40;
43      memset(rad,0,sizeof(rad));
44      for(int i=0;i<=nn;i++){
45          str[2*i+1]=40;
46         str[2*i+2]=str1[i];
47      }
48      Manacher(rad,str,n);
49          ans=1;
50     for(int i=0;i<n;i++)
51         ans=max(ans,rad[i]);
52         printf("%d\n",ans-1);
53    }
54   return 0;
55 }