usaco_calflac多行文件中找出最长回文串

usaco_calflac多行文件中找出最长回文串

回文串不考虑除字母以外的字符，并且不区分大小写。strupr()usaco不让用，可能toupper可以。strcat(s1,s2)中s1必须为数组才可以不报错。while(fgets(line,100,fin)!=NULL)读入的一行包括结尾的换行符。注意处理大小写情况。第一种方法在usaco的test8中超时了。第二种，网上查的DP方法，讨论奇偶性，高效简单快捷。

（1）暴搜。每读入一行，从此行的第一个字符起依次作为回文串的末尾判断比较。

#include < cstdio >
#include < cstdlib >
#include < cmath >
#include < iostream >
#include < algorithm >
#include < cstring >
#include < string >
#include < cctype >

using   namespace  std;
#define  MAX(a,b) (a)>(b)?(a):(b)
char  buf[ 20010 ],line[ 100 ],file[ 20010 ],str[ 2010 ] = " test " ;
int  n = 0 ,rmax = 0 ,m = 0 ;
// bool ispal(char *s1,char* s2)
// {
//     strcpy(buf,s1);
//     strupr(buf);
//      // strupr(s2);
//     while(*s1==*s2&&s2-s1>0)
//     {
//         s1++;
//         s2--;
//         while(*s1<'A'||*s1>'Z')s1++;
//         while(*s2<'A'||*s2>'Z')s2--;
//     }
//     if(s2==s1||*s2==*s1)return 1;
//     return 0;
// }
bool  ispal( char   * buf1, char *  buf2)
{
    
    int tmp=buf2-buf1+1;
        if(tmp<m)//test
                    {
                        return 0;
                    }
    while(*buf1==*buf2&&buf2-buf1>0)
    {
        buf1++;
        buf2--;
        if(*buf2<='z'&&*buf2>='a')*buf2-=32;
        if(*buf1<='z'&&*buf1>='a')*buf1-=32;
        while(*buf1<'A'||*buf1>'Z'){buf1++;n++;if(*buf1<='z'&&*buf1>='a')*buf1-=32;}
        while(*buf2<'A'||*buf2>'Z'){buf2--;n++;if(*buf2<='z'&&*buf2>='a')*buf2-=32;}
    }
    if(buf2==buf1||*buf2==*buf1)
    {
        //if(tmp>m&&tmp<n)//test
        //            {
        //                tmp=5+n;
        //            }
        return 1;
    }
    
    return 0;
}
void  cal( char *  s1, char *  s2)
{
    char* buf2,*buf1;
    /**//*while(!(*s1<='z'&&*s1>='a'||*s1<='Z'&&*s1>='A'))s1++;*/
    /**//*while(!isalpha(*s1))s1++;*/
    strcpy(buf,s1);
    //strupr(buf);
    buf1=buf;
    buf2=buf+(s2-s1);//
    char* pt=buf1;
    int t=MAX(s2-s1-2000,0);
    while(t>0)
    {
        pt++;
        t--;
    }
    int tmp;
    while(*buf2!='\0')
    {
        if(*buf2<='z'&&*buf2>='a')*buf2-=32;
        pt=buf1;
        while(buf2-pt>0)
        {
            if((tmp=buf2-pt+1)<m)break;
            if(*pt<='z'&&*pt>='a')*pt-=32;
            if(*pt==*buf2&&isalpha(*pt)&&ispal(pt,buf2))
            {
                    //tmp=buf2-pt+1;
                    
                    if(tmp>m)
                        {
                            m=tmp;
                            strcpy(str,s1+(pt-buf1));
                            *(str+m)='\0';
                            rmax=m-n;
                    //        if(rmax<0)//test
                    //{
                    //    tmp=5+n;
                    //}
                    //        
                    }
            }
            n=0;
            pt++;
        }
            buf2++;
    }
}
int  main()
     {
        FILE* fin;
        FILE* fout;
        fin=fopen("calfflac.in","r");
        fout=fopen("calfflac.out","w");
        /**//*fin=fopen("stdin","r");
        fout=fopen("stdout","w");*/
        
        //char* s="sda";
        int i,ln=0;
        int len,max=0;
        char *p;
        while(fgets(line,100,fin)!=NULL)
        //while(fgets(line,MAX,stdin)!=NULL)
        {
            
            line[strlen(line)-1]='\0';
            //fprintf(stdout,"%c\n",line[strlen(line)-1]);
            i=strlen(file);
            strcat(file,line);
            len=MAX(i-2000,0);
            p=file+len;
            //while(!isalpha(*p))p++;
            cal(p,file+i);
            //if(len>max)max=len;
        }
        fprintf(fout,"%d\n",rmax);
        //fprintf(fout,"%s\n",str);
        i=0;ln=-1;
        while(*(str+i)!='\0')
            {
                ln++;
                fprintf(fout,"%c",*(str+i));
                if(ln%80==78)fprintf(fout,"\n");
                i++;
        }
   

 #include  < cstdio >  
 #include  < string >  
 #include  < iostream >  
 #include  < algorithm >  
  using   namespace  std; 
  int  main() { 
    freopen("calfflac.in","r",stdin); 
    freopen("calfflac.out","w",stdout); 
    char a[20005],b[20005],c; 
    int ba[20005],d[20005],r=0,rpos=0; 
    int ai=0,bi=0; 
    while(scanf("%c",&c)!=EOF){ 
         a[ai]=c; 
         if(c>='a'&&c<='z'||c>='A'&&c<='Z'){ 
             b[bi]=c; 
             if(c>='A'&&c<='Z')b[bi]+='a'-'A';  
             ba[bi]=ai;//b与a的字符对应关系  
             bi++;  
         } 
         ai++;  
    } 
    d[0]=1; 
    for(int i=1;i<bi;i++){     
        if(b[i]==b[i-d[i-1]-1])d[i]=d[i-1]+2; 
        else if(b[i]==b[i-1])d[i]=2; 
        else d[i]=1; 
        if(d[i]>r){ 
             r=d[i]; 
             rpos=i; 
         }  
    } 
    printf("%d\n",r); 
     for(int i=ba[rpos-r+1];i<=ba[rpos];i++){ 
         printf("%c",a[i]); 
    } 
    printf("\n"); 
    return 0; 
 }

      if(ln%80!=78)fprintf(fout,"\n");
        /**//*fprintf(stdout,"%d\n",rmax);
        fprintf(stdout,"%s\n",str);*/
        return 0;
}

（2）DP。a为原数组，b为需考虑以判断回文的数组。ab为记录a中回文位置。