湖大 11404 manacher

链接   http://acm.hunnu.edu.cn/online/?action=problem&type=show&id=11404&courseid=0

求 最长回文个数  并且输出 ； 虽然  O(n^2) 可过； 但 O(n) 是王道

看这个博客   http://www.cnblogs.com/wulangzhou/p/3449428.html

 #include<iostream>
 #include<stdio.h>
 #include<algorithm>
 #include<cstring>
 #include<cmath>
 #define maxn 111000
 using namespace std;
 inline int min( int a,int b ){return a>b?b:a;}
 inline int max( int a,int b ){return a>b?a:b;}
 char cha[maxn],str[maxn*]; int pi[maxn*];
 struct date{
    int l,r,len;
    bool operator <(const date &a)const{
      if( a.len != len )return a.len < len;
      else return a.r < r;
    }
 }node[];
 void manacher( )
 {
     int len = strlen( str ); int mx = ; int id = ;
     memset( pi,,sizeof(pi) );
     for( int i = ; i < len; i++ )
     {
         if( mx > i )pi[i] = min( pi[id*-i],mx-i );
         else pi[i] = ;
         while( str[i-pi[i]] == str[i+pi[i]] )pi[i]++;
         node[i].l = i-(pi[i]-); node[i].r = i+(pi[i]-); node[i].len = node[i].r - node[i].l + ;
         if( i+pi[i] > mx )
         {
             mx = i+pi[i];
             id = i;
         }
     }
 }
 int main( )
 {
     int T,cas = ; scanf("%d",&T);
     while( T-- )
     {
         scanf("%s",&cha); int len = strlen( cha ); int k = ; str[k++] = '!';
         for( int i = ; i < len; i++ )
         str[k++] = '#',str[k++] = cha[i]; str[k++] = '#'; str[k] = '\0';
         manacher( );
         printf("Case #%d:\n",cas++);
         sort( node,node+k );  len = node[].len;
         if( len <=  ){continue;}
         for( int i = ; i < k; i++ )
         if( node[i].len == len )
         {
             for( int j = node[i].l; j <= node[i].r; j++ )
             if( str[j] != '#' )cout<<str[j];
             cout<<endl;
         }else break;
     }
     return ;
 }

#include<iostream>
#include<stdio.h>
#include<cstring>
#include<algorithm>
#include<cmath>
using namespace std;

char str[2100],cha[2100];
int  tab[2100];
void manacher( )
{
    int Mx = 0; int id = 0; int len = strlen(cha);
    memset(tab,0,sizeof(tab));
    for( int i = 1; i < len; i++ )
    {
        if( i < Mx )
             tab[i] = min( tab[id*2-i],Mx-i );
        else tab[i] = 1;
        while( cha[i+tab[i]] == cha[i-tab[i]] )tab[i]++;
        tab[i]--;
        if( Mx < i+tab[i] ){
            Mx = i+tab[i];
            id = i;
        }
    }
}
int main( )
{
    int T,cas = 1; cin>>T;
    while( T-- )
    {
        scanf("%s",&str); int len = strlen(str); int k = 0;
        cha[k++] = '@';
        for( int i = 0; i < len; i++ )
        {cha[k++] = '#', cha[k++] = str[i];}
         cha[k++] = '#'; cha[k] = '\0';
        int Max = 0; manacher( ); printf("Case #%d:\n",cas++);
        for( int i = 1; i < k; i++ )
        if( cha[i] != '#' )Max = max( Max,(tab[i]/2)*2+1 );
        else Max = max( Max,tab[i] );
        if( Max <= 1 ){continue;}
        for( int j = k-1; j >= 0; j-- )
        {
            if( (cha[j] == '#'&&tab[j]==Max) || (cha[j] != '#'&&(tab[j]/2)*2+1 == Max ) )
            for( int i = j-tab[j]; i != j+tab[j]; i++ )
            if( cha[i] != '#' )cout<<cha[i];
            cout<<endl;
        }
    }
    return 0;
}
/*
abacaba
*/