ACM 401 - Palindromes在线评委提供错误的答案

Question

import java.io.*;
import java.util.*;

public class Main {

public static void main(String[] args) throws IOException {
    // TODO Auto-generated method stub
    BufferedReader stdin;
    String str;

    // TODO Auto-generated method stub
    stdin = new BufferedReader(new InputStreamReader(System.in));

    char[] stringArray ;

    boolean isPalindrone, isMirrored;

    while((str = stdin.readLine())!= null) {
         //convert string into array using toCharArray() method of string class
        stringArray = str.toCharArray();

        isPalindrone =  new Main().checkPalindromes(stringArray);
        isMirrored = new Main().precheckMirroring(stringArray);

        if(isPalindrone && isMirrored) {
            System.out.println(str + " -- is a mirrored palindrome.");
        } else if(isPalindrone) {
            System.out.println(str + " -- is a regular palindrome.");
        } else if(!isPalindrone && isMirrored) {
            System.out.println(str + " -- is a mirrored string.");
        } else {
            System.out.println(str + " -- is not a palindrome.");
        }

        System.out.println();
    }
}

/* precheckpalindronetest */
public boolean precheckMirroring(char stringArray[]) {
    boolean pretest_ismirror  = true;

    char[] m_char = {'A' , 'E' , 'H', 'I' , 'J', 'L','M', 'O' ,'T','U' , 
                     'V','W' , 'X' , 'Y', 'Z'  , '1', '2','3' , '5' , '8'
    };

    boolean match = false;
    for(int i = 0 ; i < stringArray.length; ++i) {
        match = false;
        for(int j = 0 ; j < m_char.length; ++j) {
            if(stringArray[i] == m_char[j]) {
                match  = true;
                break;
            }
        }

        if(match == false) {
            pretest_ismirror = false;
            break;
        }
    }

    return pretest_ismirror;
}

/* check palindromes */
public boolean checkPalindromes(char stringArray[]) {
    int i = 0 ;
    int j = stringArray.length - 1;
    boolean check_palindrone = true;
    while(i <= j) {
        if(stringArray[i] != stringArray[j]){
            check_palindrone = false;
            break;
        }
        ++i;
        --j;
    }

    return check_palindrone;
}

 /* check mirrored */
 public boolean checkMirroredString(String str) {

        if(this.precheckMirroring(str.toCharArray()) == false) {
            return false;
        }

        StringBuffer strbuf = new StringBuffer(str);

        int inc = 0;

        Map<String, String> map = new HashMap<String, String>();

        map.put("A", "A");
        map.put("E", "3");
        map.put("H", "H");
        map.put("I", "I");
        map.put("J", "L");
        map.put("L", "J");
        map.put("M", "M");
        map.put("O", "O");
        map.put("T", "T");
        map.put("U", "U");
        map.put("V", "V");
        map.put("W", "W");
        map.put("X", "X");
        map.put("Y", "Y");
        map.put("Z", "5");
        map.put("1", "1");
        map.put("2", "S");
        map.put("3", "E");
        map.put("5", "Z");
        map.put("8", "8");

        int i = 0 ;
        int j = strbuf.length() - 1;
        while(i < j) {

            String left = Character.toString(strbuf.charAt(i));
            String right = Character.toString(strbuf.charAt(j));

            // If the character is reverse to each other
            if(map.get(left) !=  right || map.get(right) != left ){
                return false;   
            } 

            if( left != right) {
                return false;
            }

            ++i;
            --j;
        }

     return true;
   }
}

在线评委给出了错误的答案。

Answer 1

可能

    isMirrored = new Main().precheckMirroring(stringArray);

应该是

    isMirrored = new Main().checkMirroredString(stringArray);

此外 - 您无法使用==可靠地比较字符串，您应该使用equals。

另外，在checkMirroredString你可能不想要：

        if( left != right) {
            return false;
        }

Answer 2

这是我的解决方案，被在线评委接受。问题陈述的pdf版本是错误的，这简直是一种耻辱。这是链接：

http://uva.onlinejudge.org/index.php?option=com_onlinejudge&Itemid=8&page=show_problem&problem=342

非常感谢所有对我的查询做出回应的人。

import java.io.*;
import java.util.*;

public class Main{  
/**
 * @param args
 */

public Map<String, String> map;

public static void main(String[] args) throws IOException {
    // TODO Auto-generated method stub
      BufferedReader stdin;
      String str;

      // Read line
      stdin = new BufferedReader(new InputStreamReader(System.in));

      char[] stringArray ;

      boolean isPalindrone , isMirrored;

      while((str = stdin.readLine())!= null) {

            // check palindrome    
            isPalindrone =  new Main().checkPalindromes(str);
            // check mirroring
            isMirrored = new Main().checkMirrorString(str);

            if( isPalindrone ) {
                if(isMirrored) {
                    System.out.println(str + " -- is a mirrored palindrome.");
                } else {
                    System.out.println(str + " -- is a regular palindrome.");   
                }
            } 

            else {
                if(isMirrored) {    
                    System.out.println(str + " -- is a mirrored string.");
                }
                else {
                    System.out.println(str + " -- is not a palindrome.");
                }
            }   

            System.out.println(); 
         }

        }


 /* Check palindromes */
 public boolean checkPalindromes(String str) {

        char stringArray[] = str.toCharArray();

        // Always return true if length is 1
        if(stringArray.length  == 1) return true;

        int i = 0 ;
        int j = stringArray.length - 1;
        boolean check_palindrone = true;
        while(i <= j) {
            if(stringArray[i] != stringArray[j]){
                check_palindrone = false;
                break;
            }
            ++i;
            --j;
        }

        return check_palindrone;

 }

 /* Load mirrow table */
 public void initMirrorTable() {
        // Put mirror characters to hashmap     
        map = new HashMap<String, String>();
        map.put("A", "A");
        map.put("E", "3");
        map.put("H", "H");
        map.put("I", "I");
        map.put("J", "L");
        map.put("L", "J");
        map.put("M", "M");
        map.put("O", "O");
        map.put("S", "2");
        map.put("T", "T");
        map.put("U", "U");
        map.put("V", "V");
        map.put("W", "W");
        map.put("X", "X");
        map.put("Y", "Y");
        map.put("Z", "5");
        map.put("1", "1");
        map.put("2", "S");
        map.put("3", "E");
        map.put("5", "Z");
        map.put("8", "8");
 }


 /* Check mirror string */
 public boolean checkMirrorString(String str) {

        // convert it to character array
        char tochar[] = str.toCharArray();

        // Init mirror table
        this.initMirrorTable();

        boolean is_mirrorstr = false;


        // Replace each character with it's mirror character
        for(int i = 0 ; i < tochar.length ; i++) {

            // Get the reverse character
            String temp_str = map.get(Character.toString(tochar[i]));

            // if Not found then return false
            if( temp_str == null )  { return false; }

            char reverse_char = temp_str.charAt(0); 
            tochar[i] = reverse_char;

        }

        String rev = String.valueOf(tochar);
        StringBuffer mirror  = new StringBuffer(rev).reverse();

        if(str.equals(mirror.toString())) is_mirrorstr = true;

        return is_mirrorstr;

}


 }