Calf Flac

Problem：Calf Flac

It is said that if you give an infinite number of cows an infinite number of heavy-duty laptops (with very large keys), that they will ultimately produce all the world's great palindromes. Your job will be to detect these bovine beauties.

Ignore punctuation, whitespace, numbers, and case when testing for palindromes, but keep these extra characters around so that you can print them out as the answer; just consider the letters `A-Z' and `a-z'.

Find the largest palindrome in a string no more than 20,000 characters long. The largest palindrome is guaranteed to be at most 2,000 characters long before whitespace and punctuation are removed.

PROGRAM NAME: calfflac

INPUT FORMAT

A file with no more than 20,000 characters. The file has one or more lines. No line is longer than 80 characters (not counting the newline at the end).

SAMPLE INPUT (file calfflac.in)

Confucius say: Madam, I'm Adam.

OUTPUT FORMAT

The first line of the output should be the length of the longest palindrome found. The next line or lines should be the actual text of the palindrome (without any surrounding white space or punctuation but with all other characters) printed on a line (or more than one line if newlines are included in the palindromic text). If there are multiple palindromes of longest length, output the one that appears first.

SAMPLE OUTPUT (file calfflac.out)

11
Madam, I'm Adam

 

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My Answer:

/* ID:iby071 PROG:calfflac LANG:C++ */ #include<iostream> #include<fstream> #include<ctype.h> //isalpha函数所属的库 #include<cstring> using namespace std; bool equal(char a,char b) { if((a-'a'==b-'a')||(a-'a'==b-'A')||(a-'A'==b-'a')||(a-'A'==b-'A')) //注意:此题目要求不区分大小写 return true; else return false; } void getPal(char *s,int size,int &left,int &right,int &length) { int l=left,r=right; bool flag=true; do { while(left>=0 && isalpha(s[left])==0) --left; //忽略非字母的字符 while(right<size && isalpha(s[right])==0) ++right; if(left>=0 && right<size && equal(s[left],s[right]) ) { length+=2; l=left; r=right;} else flag=false; --left; ++right; }while(flag); left=l; right=r; } int main() { ifstream fin("calfflac.in"); ofstream fout("calfflac.out"); char string[20001]; int size,length,left=0,right=0,low=0,high=0,max=1,j; fin.getline(string,20000,'@'); size=strlen(string); for(int i=0;i<size;i=j) { while(i<size && isalpha(string[i])==0) ++i; left=i; if(i>=size) break; ++i; while(i<size && isalpha(string[i])==0) ++i; j=i; if(equal(string[left],string[i])) //偶数个字母的calfflac的情况 { right=i; length=0; getPal(string,size,left,right,length); if (length>max){ max=length; low=left; high=right;} } else //奇数个字母的情况 { if(i>=size) break; ++i; while(i<size && isalpha(string[i])==0) ++i; if(equal(string[left],string[i])) { right=i; length=1; getPal(string,size,left,right,length); if (length>max){ max=length; low=left; high=right;} } } } if(max==1) {fout<<max<<endl<<string[0]<<endl;} else { fout<<max<<endl; for(int i=low;i<=high;++i) fout<<string[i]; fout<<endl; } return 0; }