Manacher模板

预处理：

T[0] = '$';
int len = strlen(S);
for ( int i=1 ; i<=len ; i++ )
{
    T[i*2-1] = '#';
    T[i*2] = S[i-1];
}
T[len*2+1] = '#';
T[len*2+2] = '\0';

模板：

int Manacher( char *s , int *p )
{
    p[0] = 0;
    int len = strlen(s);
    int res = 0,mx = 0,pos;
    for ( int i=1 ; i<len ; i++ )
    {
        if ( i<mx ) p[i] = min( p[pos*2-i] , mx-i );
        else p[i] = 1;
        while( s[i-p[i]]==s[i+p[i]] ) p[i]++;
        if ( i+p[i]>mx ) mx = i+p[i],pos = i;
        res = max ( res , p[i] );
    }
    return res-1;
}