implement intPartitions method in MainExercises

src/main/java/MainExercises.java

@@ -1,3 +1,5 @@
+import java.util.ArrayList;
+
 public class MainExercises
 {
     public char[][] generateTriangle(int n) {
@@ -61,37 +63,60 @@ public class MainExercises
         return result;
     }
 
-    /*
-        integer partitioning is a combinatorics problem in discreet maths
-        the problem is to generate sum numbers which their summation is the input number
-
-        e.g. 1 -> all partitions of integer 3 are:
-        3
-        2, 1
-        1, 1, 1
-
-        e.g. 2 -> for number 4 goes as:
-        4
-        3, 1
-        2, 2
-        2, 1, 1
-        1, 1, 1, 1
-
-        Note: As you can see in the examples, we want to generate distinct partitions,
-        which means 1,2 and 2,1 are not different — they count as the same combination.
-
-        You should generate all partitions of the input number.
-
-        Hint: You can determine the size and order of the arrays by finding the pattern
-        of partitions and their count. Trust me, this one's fun and easy :)
-
-        If you're familiar with Lists and ArrayLists, you can also edit the method's
-        body to use them instead of arrays.
-    */
-
     public int[][] intPartitions(int n) {
-        // todo
-        return null;
+        int[][] result;
+        ArrayList<ArrayList<Integer>> mainArray = new ArrayList<>();
+
+        ArrayList<Integer> start = new ArrayList<>();
+        start.add(n);
+        mainArray.add(start);
+        
+        while (true) { 
+            ArrayList<Integer> latestArray = mainArray.get(mainArray.size() - 1);
+
+            Integer numberOfInterest = 0;
+            for (Integer number : latestArray)
+            {
+                if (number > 1) {
+                    numberOfInterest = number;
+                    break;
+                }
+            }   
+
+            if (numberOfInterest == 0) break;
+
+            numberOfInterest--;
+            Integer remain = n - numberOfInterest;
+            ArrayList<Integer> newArray = new ArrayList<>();
+            newArray.add(numberOfInterest);
+
+            for (Integer number = numberOfInterest;;) {
+                if (number >= remain) {
+                    newArray.add(remain);
+                    break;
+                }
+                else {
+                    newArray.add(number);
+                    remain -= number;
+                }
+            }
+
+            mainArray.add(newArray);
+        }
+
+        result = new int[mainArray.size()][];
+
+        for (int i = 0; i < mainArray.size(); i++) {
+            ArrayList<Integer> array = mainArray.get(i);
+
+            result[i] = new int[array.size()];
+
+            for (int j = 0; j < array.size(); j++) {
+                result[i][j] = array.get(j);
+            }
+        }
+
+        return result;
     }