Merge pull request blakeembrey#124 from roitt/hotel-room

Hotel Room solution JAVA.

solutions/java/HotelRoom.java

@@ -0,0 +1,72 @@
+import java.util.ArrayList;
+
+public class HotelRoom {
+	public static void main(String[] args) {
+		HotelRoom hr = new HotelRoom();
+		Integer found = hr.getRoomNumber(100);
+		if (found != null)
+			System.out.print(found);
+	}
+
+	public Integer getRoomNumber(int n) {
+		for (int i = 2; i <= n; i = i + 2) {
+			// We know off the bat that its not a prime number, nor an odd number.
+			ArrayList<Integer> factors = new ArrayList<Integer>();
+			int index = 1;
+			int factorSum = 0;
+			while (index <= i / 2) {
+				// If i is a factor
+				if (i % index == 0) {
+					factorSum += index;
+					factors.add(index);
+				}
+				index++;
+			}
+			// We have the sum of factors here. Check if its greater than the
+			// number itself.
+			if (factorSum > i) {
+				// Find sums of all the subsets of the factors
+				Integer foundNumber = checkSubsetSum(factors, i);
+				if (foundNumber != null)
+					return foundNumber;
+				else
+					continue;
+			} else {
+				continue;
+			}
+		}
+		return null;
+	}
+
+	public Integer checkSubsetSum(ArrayList<Integer> factors, int n) {
+		ArrayList<ArrayList<Integer>> result = new ArrayList<ArrayList<Integer>>();
+		for (Integer i : factors) {
+			ArrayList<ArrayList<Integer>> temp = new ArrayList<ArrayList<Integer>>();
+			// Get all the elements already in the result
+			for (ArrayList<Integer> a : result)
+				temp.add(new ArrayList<Integer>(a));
+
+			// Add i to each of these subsets
+			for (ArrayList<Integer> a : temp)
+				a.add(i);
+
+			// Add i by itself
+			ArrayList<Integer> single = new ArrayList<Integer>();
+			single.add(i);
+			temp.add(single);
+			result.addAll(temp);
+		}
+
+		boolean matched = true;
+		for (ArrayList<Integer> al : result) {
+			int sum = 0;
+			for (Integer i : al)
+				sum += i;
+			if (sum == n)
+				matched = false;
+		}
+		if (matched)
+			return n;
+		return null;
+	}
+}