hdu3068 longest palindrome (Manacher algorithm)

Test instructions

The longest palindrome sequence in a string, given a string

Problem Solving Ideas:

Manacher algorithm

Time complexity: O (N)

Code:

#include <cstdio> #include <cstring> #include <algorithm> #define MAXN 110010using namespace Std;char b [Maxn],a[maxn<<1];int p[maxn<<1];int N;int Main () {while    (scanf ("%s", &b[1])!=eof) {        int i;        for (i=1;b[i]!= ' n '; ++i) {            a[(i<<1)]=b[i];            a[(i<<1) +1]= ' # ';        }        a[0]= '? ';        a[1]= ' # ';        N= (i<<1) +2;        a[n]=0;        int maxid,maxl,id;        maxid=maxl=0;        memset (P,0,sizeof (P));        for (int i=1;i<n;++i) {            if (maxid>i)                p[i]=min (p[2*id-i],maxid-i);            else                p[i]=1;            while (A[i+p[i]]==a[i-p[i]])                p[i]++;            if (P[i]+i>maxid)            {                maxid=p[i]+i;                id=i;            }            if (P[I]>MAXL)                maxl=p[i];        }        printf ("%d\n", MaxL-1);    }    return 0;}

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hdu3068 longest palindrome (Manacher algorithm)