HDU 4513 吉哥系列故事——完美队形II

从中间向两边递减的回文，特判一下就好

#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
using namespace std;
const int qq=100000+10;
int que[qq*2];
int p[qq*2];
int main()
{
    int t;scanf("%d",&t);
    while(t--){
        int n;scanf("%d",&n);
        int w=2;
        que[0]=20;
        que[1]=1000;
        for(int i=0;i<n;++i){
            scanf("%d",&que[w++]);
            que[w++]=1000;
        } 
        n=n*2+1;
        int maxn=0;
        int mx=0;
        int id;
        //for(int i=0;i<=n;++i)
        //    printf("%d ",que[i]);
        //    printf("
");
        for(int i=1;i<n;++i){
            if(mx>i)
                p[i]=min(mx-i,p[2*id-i]);
            else
                p[i]=1;
            while(que[i+p[i]]==que[i-p[i]]&&(que[i-p[i]]==1000||que[i-p[i]]<=que[i-p[i]+2]))
                p[i]++;
            if(i+p[i]>mx){
                mx=i+p[i];
                id=i;
            }
            if(p[i]-1>maxn)
                maxn=p[i]-1;
            //printf("%d ",p[i]);
        }
        //printf("
");
        printf("%d
",maxn);
    }
    return 0;
}