Bzoj 2565 longest Double palindrome string hash+ two points

Topic: Given a string, to find the longest substring, the string can be decomposed into two palindrome substrings

Stupid, I forgot how manacher wrote = = Helpless hash+ two points

First multiply the string with a delimiter and then find the longest palindrome radius centered at each point

Then consider how two palindrome strings merge into one

We find that the j-i of the I-centered palindrome and the J-centric palindrome combine to the length of

The prerequisite for merging is the intersection of a palindrome with a two-point center.

So for each J we ask for the leftmost I with the intersection

Maintain a suffix min just screw it up.

#include <cstdio> #include <cstring> #include <iostream> #include <algorithm> #define M 200200# Define BASE 131using namespace Std;typedef unsigned long long ll;int n,ans;int F[m],min_pos[m];char s[m];ll hash1[m],hash2 [M],power[m];bool Judge (int mid,int len) {ll _hash1=hash1[mid+len-1]-hash1[mid-1]*power[len];ll _hash2=hash2[mid-len +1]-hash2[mid+1]*power[len];return _hash1==_hash2;} int bisecition (int x) {int l=1,r=min (x,n-x+1), while (l+1<r) {int mid=l+r>>1;if (Judge (x,mid)) L=mid;elser=mid;} Return Judge (x,r)? R:l;} int main () {int i;static char str[m];scanf ("%s", str+1); for (s[1]= ' # ', i=1;str[i];i++) s[i<<1]=str[i],s[i<< 1|1]= ' # '; N=strlen (s+1); for (power[0]=1,i=1;i<=n;i++) power[i]=power[i-1]*base;for (i=1;i<=n;i++) hash1[i]= Hash1[i-1]*base+s[i];for (i=n;i;i--) hash2[i]=hash2[i+1]*base+s[i];memset (min_pos,0x3f,sizeof min_pos); for (i=1;i <=n;i++) {f[i]=bisecition (i); Min_pos[i+f[i]-1]=min (min_pos[i+f[i]-1],i);} for (i=n-1;i;i--) min_pos[i]=min (min_pos[i],min_pos[I+1]); for (i=1;i<=n;i++) {int Temp=min_pos[i-f[i]+1];ans=max (ans,i-temp<<1);} cout<< (ans>>1) <<endl;return 0;}

Bzoj 2565 longest Double palindrome string hash+ two points