Программирование, Путешествия, Покер

Римское число читаем справа налево, если встретили единичку, то сразу добавляем, если любое другое число, то смотрим число слева от него(при условии, что оно есть) и добавляем сколько нужно.

import java.util.Scanner;

public class Romans_to_Decimals
{
public static void main(String[] args)
{
System.out.println("Enter roman number from I to MMMCMXCIX (1 to 3999), q to quit: ");
Scanner in = new Scanner(System.in);

boolean done = false;
while (!done && in.hasNext())
{
String number = in.next();
if (number.equals("q"))
{
done = true;
}
else
{
int result = 0;
char[] array = number.toCharArray();

for (int i = number.length() - 1; i >= 0; i--)
{
switch ( array )
{
case 'I':
result += 1;
break;
case 'X':
if (i != 0 && array[i-1] == 'I') //IX = 9
{
result += 9;
i--;
}
else
{
result += 10;
}
break;
case 'C':
if (i != 0 && array[i-1] == 'X') //XC = 90
{
result += 90;
i--;
}
else
{
result += 100;
}
break;
case 'M':
if (i != 0 && array[i-1] == 'C') //CM = 900
{
result += 900;
i--;
}
else
{
result += 1000;
}
break;
case 'V':
if (i != 0 && array[i-1] == 'I') //IV = 4
{
result += 4;
i--;
}
else
{
result += 5;
}
break;
case 'L':
if (i != 0 && array[i-1] == 'X') //XL = 40
{
result += 40;
i--;
}
else
{
result += 50;
}
break;
case 'D':
if (i != 0 && array[i-1] == 'C') //CD = 400
{
result += 400;
i--;
}
else
{
result += 500;
}
break;
default:
System.out.println("Not correct roman number");
break;
}
}
System.out.println("Corresponding decimal number is: " + result);
}
}
in.close();
}
}[/i][/i][/i][/i][/i][/i]

import java.util.Scanner;

public class Decimals_to_Romans
{
public static String unitConverter(int remainder)
{
switch(remainder)
{
case 1: return "I";
case 2: return "II";
case 3: return "III";
case 4: return "IV";
case 5: return "V";
case 6: return "VI";
case 7: return "VII";
case 8: return "VIII";
case 9: return "IX";
default: return "";
}
}

public static String decimalConverter(int remainder)
{
switch(remainder)
{
case 1: return "X";
case 2: return "XX";
case 3: return "XXX";
case 4: return "XL";
case 5: return "L";
case 6: return "LX";
case 7: return "LXX";
case 8: return "LXXX";
case 9: return "XC";
default: return "";
}
}

public static String hundredsConverter(int remainder)
{
switch(remainder)
{
case 1: return "C";
case 2: return "CC";
case 3: return "CCC";
case 4: return "CD";
case 5: return "C";
case 6: return "DC";
case 7: return "DCC";
case 8: return "DCCC";
case 9: return "CM";
default: return "";
}
}

public static String thousandsConverter(int remainder)
{
switch(remainder)
{
case 1: return "M";
case 2: return "MM";
case 3: return "MMM";
default: return "";
}
}

public static void main(String[] args)
{
System.out.println("Enter decimal number from 1 to 3999, -1 to quit: ");
Scanner in = new Scanner(System.in);

boolean done = false;
while (!done && in.hasNextInt())
{
Integer number = in.nextInt();
if (number == -1)
{
done = true;
}
else
{
String result = "";
int digitNumber = 1;
int numberLength = number.toString().length();
for (int i = 1; i <= numberLength; i++)
{
int remainder = number % 10;
switch (digitNumber)
{
case 1: result = unitConverter(remainder); break;
case 2: result = decimalConverter(remainder) + result; break;
case 3: result = hundredsConverter(remainder) + result; break;
case 4: result = thousandsConverter(remainder) + result; break;
}
number /= 10;
digitNumber++;
}


System.out.println("Corresponding roman number is: " + result);
}
}
in.close();
}
}

public class RomeToArabicConverter {

public static int convertRomeToArabic(String romeNumber) {
if (romeNumber == null || !romeNumber.matches("\\bM{0,4}(CM|CD|D?C{0,3})(XC|XL|L?X{0,3})(IX|IV|V?I{0,3})\\b")) {
throw new IllegalArgumentException("invalid number");
}

int result = 0;
for (int i = romeNumber.length() - 1; i > -1; i--) {
int current = getValueForLetter(romeNumber, i);
int prev = getValueForLetter(romeNumber, i - 1);
if (current > prev) {
result -= prev;
i--;
}
result += current;
}
return result;
}

private static int getValueForLetter(String number, int index) {
if (index < 0) {
return -1;
}
switch (number.charAt(index)) {
case 'I':
return 1;
case 'V':
return 5;
case 'X':
return 10;
case 'L':
return 50;
case 'C':
return 100;
case 'D':
return 500;
case 'M':
return 1000;
default:
throw new IllegalArgumentException("Invalid letter");
}
}

}