manacher板子

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hdu5371
http://acm.hdu.edu.cn/showproblem.php?pid=5371

#include <cstdio>#include <iostream>#include <algorithm>#define MAXN 100010using namespace std;int n;int d[MAXN];int st[MAXN*2];int p[MAXN*2];int len;void manacher(){    int MaxId=0,id;    for(int i=0; i<len; i++)    {        if(MaxId>i)            p[i]=min(p[2*id-i],MaxId-i);        else            p[i]=1;        while(st[i+p[i]]==st[i-p[i]])            p[i]++;        if(p[i]+i>MaxId)        {            id=i;            MaxId=p[i]+i;        }    }}int main(){    int T;    scanf("%d",&T);    for(int t=1; t<=T; t++)    {        scanf("%d",&n);        for(int i = 0; i <= 2*n+1; i++)            p[i] =0;        len = 0;        st[len++]= -2;        st[len++]= -1;        for(int i=1; i<=n; ++i)        {            scanf("%d",&st[len++]);            st[len++] = -1;        }        st[len] = 0;        manacher();        int maxans=1;        for(int i = 3; i < len; i+=2)            for(int j = maxans; j <= p[i]; j+=2)            {                if(p[j+i-1] >= j)                    maxans = j;            }            printf("Case #%d: %d\n",t,(maxans)/2*3);    }    return 0;}</span>

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