BZOJ 2565: 最长双回文串

智商康复计划。。。。。。。。

#include<iostream>#include<cstdio>#include<cstring>#include<algorithm>#include<vector>#include<cmath>using namespace std;#define rep(i,l,r) for(int i=l;i<=r;i++)#define per(i,r,l) for(int i=r;i>=l;i--)#define mmt(a,v) memset(a,v,sizeof(a))const int N=100000+5;char s[N<<1],t[N];int n;int r[N<<1],a[N<<1],b[N<<1];int manacher(){int m=n<<1|1;rep(i,1,m)if(i&1)s[i]='#';else s[i]=t[i>>1];s[m]='#';int id=0,mx=0;rep(i,1,m){if(mx>i)r[i]=min(mx-i,r[2*id-i]);else r[i]=1;while(i-r[i]>=1&&i+r[i]<=m&&s[i-r[i]]==s[i+r[i]])r[i]++;if(i+r[i]>mx)mx=i+r[i],id=i;}int j=1;rep(i,1,m){while(j+r[j]<=i)j++;a[i]=j;}j=m;per(i,m,1){while(j-r[j]>=i)j--;b[i]=j;}int ans=0;rep(i,1,m)if(i&1)ans=max(ans,b[i]-a[i]);return ans;}int main(){//freopen("a.in","r",stdin);scanf("%s",t+1);n=strlen(t+1);printf("%d\n",manacher());return 0;}