implement intPartitions function in MainExercises

src/main/java/MainExercises.java

@@ -1,3 +1,6 @@
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
 public class MainExercises
 {
 
@@ -44,8 +47,29 @@ public class MainExercises
 
 
     public int[][] intPartitions(int n) {
-        // todo
-        return null;
+        List<int[]> result = new ArrayList<>();
+        int[] partition = new int[n];
+        int length = 0;
+        partition[length] = n;
+        while (true) {
+            result.add(Arrays.copyOf(partition, length+1));
+            int rem = 0;
+            while (length >= 0 && partition[length] == 1){
+                rem += partition[length];
+                length--;
+            }
+            if ( length < 0 ) break;
+            partition[length]--;
+            rem++;
+            while (rem > partition[length]) {
+                partition[length+1] = partition[length];
+                rem -= partition[length];
+                length++;
+            }
+            partition[length+1] = rem;
+            length++;
+        }
+        return result.toArray(new int[0][]);
     }