Assignment Finished

src/RomanNumerals.java

@@ -1,8 +1,113 @@
+import java.util.ArrayList;
 
 public class RomanNumerals {
-	public int convertToInteger(String romanNum) {
-		// To be Implemented
-		return 0;
+
+	public int convertToInteger(String romanNum) throws RomanNumeralsInvalidFormatException {
+		int i, res = 0, temp;
 
+		if (!invalidFormatCheck(romanNum)) {
+			throw new RomanNumeralsInvalidFormatException();
+		}
+
+		ArrayList<Integer> splited = splitGroup(romanNum);
+
+		if (!invalidSubtractCheck(splited)) {
+			throw new RomanNumeralsInvalidFormatException();
+		}
+
+		return calculateResult(splited);
+	}
+
+	private int calculateResult(ArrayList<Integer> splited) {
+		int i, res=0, temp;
+		int lastindex = splited.size() - 1;
+		int lastvalue = splited.get(lastindex);
+		for (i=lastindex;i>=0;i--) {
+			temp = splited.get(i);
+			if (temp >= lastvalue) {
+				res += temp;
+			}
+			else {
+				res -= temp;
+			}
+			lastvalue = temp;
+		}
+		return res;
+	}
+
+	private ArrayList<Integer> splitGroup(String romanNum) {
+		ArrayList<Integer> result = new ArrayList<Integer>();
+		int i, count=0;
+		int current = getValue(romanNum.charAt(0));
+		for (i=0;i<romanNum.length();i++) {
+			if (current == getValue(romanNum.charAt(i))) {
+				count++;
+			}
+			else {
+				result.add(count*current);
+				count = 1;
+				current = getValue(romanNum.charAt(i));
+			}
+		}
+		result.add(count*current); //last one
+		return result;
+	}
+
+	private boolean invalidSubtractCheck(ArrayList<Integer> romanList) {
+		int lastindex = romanList.size() - 1;
+		int lastvalue = romanList.get(lastindex);
+		int i, temp;
+		for (i=lastindex-1;i>=0;i--) {
+			temp = romanList.get(i);
+			if ((temp < lastvalue && (!isnotFive(temp))) || (temp*10 < lastvalue)) {
+				//only 1, 10, 100 allowed as subtractor
+				//I can be subtracted from maximum 10, X from 100, ...
+				return false;
+			}
+		}
+		return true;
+	}
+
+	private boolean invalidFormatCheck(String romanNum) {
+		int lastindex = romanNum.length() - 1;
+		char last = romanNum.charAt(lastindex);
+		int i, count=1;
+		for (i=lastindex-1;i>=0;i--) {
+			if (romanNum.charAt(i)==last) {
+				count += 1;
+				if (!isnotFive(getValue(last)) || count > 3) {
+					return false;
+				}
+			}
+			else if (getValue(romanNum.charAt(i)) == 0) {
+				//default value, invalid character
+				return false;
+			}
+			else {
+				count = 1;
+			}
+
+		}
+		return true;
+	}
+
+	private boolean isnotFive(int c) {
+		if (c == 1 || c == 10 || c == 100 || c == 1000) {
+			return true;
+		}
+		return false;
+	}
+
+	private static int getValue(char a) {
+		switch(a) {
+			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: return 0;
+		}
 	}
 }

src/RomanNumeralsInvalidFormatException.java

@@ -0,0 +1,4 @@
+
+public class RomanNumeralsInvalidFormatException extends Exception {
+
+}