implement intPartitions method

src/main/java/MainExercises.java

@@ -1,3 +1,5 @@
+import java.util.ArrayList;
+
 public class MainExercises
 {
     public char[][] generateTriangle(int n) {
@@ -66,37 +68,36 @@ 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;
+        ArrayList<int[]> result = new ArrayList<>();
+        ArrayList<Integer> curPartition = new ArrayList<>();
+
+        fillPartition(n, n, curPartition, result);
+
+        return result.toArray(new int[result.size()][]);
+    }
+
+    private void fillPartition(int max, int remaining, ArrayList<Integer> curPartition, ArrayList<int[]> result) {
+        if (remaining == 0) {
+            int size = curPartition.size();
+            int[] savingArr = new int[size];
+
+            for (int i = 0; i < size; i++) {
+                savingArr[i] = curPartition.get(i);
+            }
+
+            result.add(savingArr);
+            return;
+        }
+
+        for (int i = Math.min(max, remaining); i >= 1; i--) {
+            curPartition.add(i);
+            int newRemaining = remaining - i;
+
+            fillPartition(i, newRemaining, curPartition, result);
+
+            curPartition.removeLast();
+        }
     }