Question

尝试编写程序以读取表示罗马数字（来自用户输入）的字符串，然后将其转换为阿拉伯语形式（整数）。例如，I = 1，V = 5，X = 10等。

基本上，采用String类型参数的构造函数必须将字符串（来自用户输入）解释为罗马数字，并将其转换为相应的int值。

除了正在进行的以下（还没有编译）之外，是否有更简单的方法来解决这个问题：

import java.util.Scanner;

public class RomInt {
String roman;
int val;
void assign(String k)
{
  roman=k;
}

private class Literal
{
    public char literal;
    public int value;

    public Literal(char literal, int value)
    {
        this.literal = literal;
        this.value = value;
    }
}

private final Literal[] ROMAN_LITERALS = new Literal[]
        {
                new Literal('I', 1),
                new Literal('V', 5),
                new Literal('X', 10),
                new Literal('L', 50),
                new Literal('C', 100),
                new Literal('D', 500),
                new Literal('M', 1000)
        };

public int getVal(String s) {

   int holdValue=0;

        for (int j = 0; j < ROMAN_LITERALS.length; j++)
        {
            if (s.charAt(0)==ROMAN_LITERALS[j].literal)
            {
                       holdValue=ROMAN_LITERALS[j].value;
                           break;
            }  //if()
        }//for()

  return holdValue;
}  //getVal()
public int count()
{
   int count=0;
   int countA=0;
   int countB=0;
   int lastPosition = 0;
    for(int i = 0 ; i < roman.length(); i++)
    {
      String s1 = roman.substring(i,i+1);
        int a=getVal(s1);
        countA+=a;
    }
    for(int j=1;j<roman.length();j++)
    {
        String s2=  roman.substring(j,j+1);
        String s3=  roman.substring(j-1,j);
        int b=getVal(s2);
        int c=getVal(s3);
        if(b>c)
        {
            countB+=c;
        }
    }
    count=countA-(2*countB);
    return count;
    }


void disp()
{

     int result=count();
    System.out.println("Integer equivalent of "+roman+" = " +result);
}


  public static void main(String[] args)
{
Scanner keyboard = new Scanner(System.in);
System.out.print("Please enter Roman Symbol:");
String s = keyboard.nextLine();
RomInt();

}

}

Answer 1

Roman numerals/Decode Example:

class Roman {

    private static int decodeSingle(char letter) {
        switch (letter) {
            case 'M':
                return 1000;
            case 'D':
                return 500;
            case 'C':
                return 100;
            case 'L':
                return 50;
            case 'X':
                return 10;
            case 'V':
                return 5;
            case 'I':
                return 1;
            default:
                return 0;
        }
    }

    public static int decode(String roman) {
        int result = 0;
        String uRoman = roman.toUpperCase(); //case-insensitive
        for (int i = 0; i < uRoman.length() - 1; i++) {//loop over all but the last character
            if (decodeSingle(uRoman.charAt(i)) < decodeSingle(uRoman.charAt(i + 1))) {
                result -= decodeSingle(uRoman.charAt(i));
            } else {
                result += decodeSingle(uRoman.charAt(i));
            }
        }
        result += decodeSingle(uRoman.charAt(uRoman.length() - 1));
        return result;
    }

    public static void main(String[] args) {
        System.out.println(decode("MCMXC")); //1990
        System.out.println(decode("MMVIII")); //2008
        System.out.println(decode("MDCLXVI")); //1666
    }
}

Answer 2

使用enum，轻松简单的解决方案。首先在罗马时定义十进制等效权重。

enum Roman{
    i(1),iv(4),v(5), ix(9), x(10);
    int weight;

    private Roman(int weight) {
        this.weight = weight;
    }
};

这是将十进制转换为罗马字符串的方法。

static String decToRoman(int dec){
    String roman="";
    Roman[] values=Roman.values();
    for (int i = values.length-1; i>=0; i--) {
       while(dec>=values[i].weight){
           roman+=values[i];
           dec=dec-values[i].weight;
       }            
    }
    return roman;
}

Answer 3

您可以尝试使用Hashmap存储罗马数字和等效的阿拉伯数字。

HashMap test = new HashMap（）;

test.add("I",1);
test.add("V",5);
test.add("X",10);
test.add("L",50);
test.add("C",100);
test.add("D",500);
test.add("M",1000);
//This would insert all the roman numerals as keys and their respective arabic numbers as 
  values.

要检索用户输入的相应阿拉伯数字，您可以使用以下代码：

Scanner sc = new Scanner(System.in);
System.out.println(one.get(sc.next().toUpperCase()));
//This would print the respective value of the selected key.This occurs in O(1) time.

<强>其次，

如果您只有这些罗马数字集，那么您可以选择简单的switch case语句。

switch(sc.next().toUpperCase())
{
case 'I' :
     System.out.println("1");
     break;
case 'V'
     System.out.println("5");
     break;
.
.
.
& so on 
}

希望这有帮助。

Answer 4

这个怎么样：

public static int convertFromRoman(String roman) {
    Map<String, Integer> v = new HashMap<String, Integer>();
    v.put("IV", 4);
    v.put("IX", 9);
    v.put("XL", 40);
    v.put("CD", 400);
    v.put("CM", 900);
    v.put("C", 100);
    v.put("M", 1000);
    v.put("I", 1);
    v.put("V", 5); 
    v.put("X", 10);
    v.put("L", 50);
    v.put("D", 500);
    int result = 0;
    for (String s : v.keySet()) {
     result += countOccurrences(roman, s) * v.get(s);
     roman = roman.replaceAll(s, "");
    }

    return result;
}



public static int countOccurrences(String main, String sub) {
   return (main.length() - main.replace(sub, "").length()) / sub.length();
}

我不确定我是否拥有所有可能的组合，因为我不是罗马数字的专家。只需确保您减去的位置在地图中排在第一位。

Answer 5

您的编译问题可以通过以下代码解决。但肯定没有优化它：

public static void main(String[] args)
{
    Scanner keyboard = new Scanner(System.in);
    System.out.print("Please enter Roman Symbol:");
    String s = keyboard.nextLine();

    RomInt temp = new RomInt();
    temp.getVal(s);
    temp.assign(s);
    temp.disp();
}

罗马数字到数字转换

5 个答案: