【算法】HDOJ-1048  The Hardest Problem Ever

 //杭电ACM - 1048

The Hardest Problem Ever

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 65536/32768 K (Java/Others)
Total Submission(s): 11958    Accepted Submission(s): 5400

Problem Description
Julius Caesar lived in a time of danger and intrigue. The hardest situation Caesar ever faced was keeping himself alive. In order for him to survive, he decided to create one of the first ciphers. This cipher was so incredibly sound, that no one could figure it out without knowing how it worked.
You are a sub captain of Caesar's army. It is your job to decipher the messages sent by Caesar and provide to your general. The code is simple. For each letter in a plaintext message, you shift it five places to the right to create the secure message (i.e., if the letter is 'A', the cipher text would be 'F'). Since you are creating plain text out of Caesar's messages, you will do the opposite:

Cipher text
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

Plain text
V W X Y Z A B C D E F G H I J K L M N O P Q R S T U

Only letters are shifted in this cipher. Any non-alphabetical character should remain the same, and all alphabetical characters will be upper case.
 

Input
Input to this problem will consist of a (non-empty) series of up to 100 data sets. Each data set will be formatted according to the following description, and there will be no blank lines separating data sets. All characters will be uppercase.

A single data set has 3 components:

Start line - A single line, "START"

Cipher message - A single line containing from one to two hundred characters, inclusive, comprising a single message from Caesar

End line - A single line, "END"

Following the final data set will be a single line, "ENDOFINPUT".
 

Output
For each data set, there will be exactly one line of output. This is the original message by Caesar.
 

Sample Input

START NS BFW, JAJSYX TK NRUTWYFSHJ FWJ YMJ WJXZQY TK YWNANFQ HFZXJX END START N BTZQI WFYMJW GJ KNWXY NS F QNYYQJ NGJWNFS ANQQFLJ YMFS XJHTSI NS WTRJ END START IFSLJW PSTBX KZQQ BJQQ YMFY HFJXFW NX RTWJ IFSLJWTZX YMFS MJ END ENDOFINPUT

 

Sample Output

IN WAR, EVENTS OF IMPORTANCE ARE THE RESULT OF TRIVIAL CAUSES I WOULD RATHER BE FIRST IN A LITTLE IBERIAN VILLAGE THAN SECOND IN ROME DANGER KNOWS FULL WELL THAT CAESAR IS MORE DANGEROUS THAN HE

 

Source
South Central USA 2002

 

 

My code

#include <iostream>using namespace std; int main(){    int i,j;    string line = "a",line2 = "a";    char c;     while( getline(cin,line) ){           //排错：读取第一行字符串，赋给word。如果读取失败，退出循环。         if(line == "ENDOFINPUT") return 0;    //排错：如果新的一组开头是“ENDOFINPUT”，return 0,程序结束。此时word值为“ENDOFINPUT”。        else if(line == "START"){              //正确：如果新的一组开头是“START”，继续检测。此时word值为“START”            while( getline(cin,line) ){                if( line == "END" ) break;     //如果遇到“END”，退出循环。                 else {                         //为要翻译的语句                    line2=line;                    for(i=0;line[i]!='\0';i++){ //循环到这一句最后。                        if( 'A'<=line[i] && line[i]<='E' )                            line2[i]=line[i]+21;                        else if( 'F'<=line[i] && line[i]<='Z' )                            line2[i]=line[i]-5;                    }                }                cout<<line2<<endl;            }        }        else return 0;                          //排错：如果输入既不是START也不是ENDOFINPUT，说明有错，return0程序结束。    }    return 0;}

 

算法分析：

主要运用到getline()函数，读取每一行的字符串。

C语法：

     char buf[20]; 
     gets(buf);

C++语法：

     如果用string buf;来保存：

     getline( cin , buf );

     原型：

     istream& getline ( istream &is , string &str , char delim );

     函数在输入流is中遇到文件结束符（EOF）或者在读入字符的过程中遇到错误都会结束。

     在遇到终结符delim后，delim会被丢弃，不存入str中。在下次读入操作时，将在delim的下个字符开始读入。

     如果用char buf[ 255 ]; 来保存：
     cin.getline( buf, 255 );

 

主要思路：

     1、判断本句是否为需要翻译的语句。

     2、若是翻译。

分析：

     主要有两个while嵌套循环。

     第一个循环作用是循环“组”，并判断读取的这行是否为“START”或“ENDOFINPUT”。如果是“START”表示一个“组”开始，继续读取下一行；如果是“ENDOFINPUT”表示“组”读取结束，return 0 程序结束。

     第二个循环作用是循环“组的内容”，即组内需要翻译的部分，它可以是多行。它判断读取的新一行字符串是否为“END”。如果是，则表示需要翻译的内容结束，break跳出循环，继续下一组的循环。如果不是“END”，表示改行读取的是翻译内容。然后列一个for循环进行翻译。