implement main exercises

src/main/java/MainExercises.java

@@ -1,3 +1,6 @@
+import java.util.ArrayList;
+import java.util.List;
+
 public class MainExercises
 {
     /*
@@ -19,10 +22,24 @@ public class MainExercises
     the output has to be a two-dimensional array of characters, so don't just print the triangle!
  */
     public char[][] generateTriangle(int n) {
+        if ( n == 0){
+            return new char[0][];
+        }
 
-        // todo
-        return null;
+        char [][] triangle = new char[n][];
+        for (int x = 0; x < n; x++){
+            triangle[x] = new char[x + 1];
 
+            for (int y = 0; y <= x; y++){
+                if (y == 0 || x == y || x == n-1){
+                    triangle[x][y] = '*';
+                }
+                else {
+                    triangle[x][y] = ' ';
+                }
+            }
+        }
+        return triangle;
     }
 
 
@@ -58,8 +75,43 @@ public class MainExercises
            - Number of columns: matrix[0].length (if rectangular)
    */
     public int[] spiralTraversal(int[][] matrix) {
-        // todo
-        return null;
+        if (matrix == null || matrix.length == 0 || matrix[0].length == 0) {
+            return new int[0];
+        }
+
+        int[] path = new int[matrix.length * matrix[0].length];
+        int up = 0 ;
+        int down = matrix.length - 1;
+        int left = 0;
+        int right = matrix[0].length - 1;
+        int step = 0;
+
+        while ( up <= down && left <= right){
+            for (int i = left; i <= right; i++){
+                path[step++] = matrix[up][i];
+            }
+            up++;
+
+            for (int j = up; j <= down; j++){
+                path[step++] = matrix[j][right];
+            }
+            right--;
+
+            if (up <= down){
+                for (int i = right; i >=left; i--){
+                    path[step++] = matrix[down][i];
+                }
+                down--;
+            }
+
+            if (right >= left){
+                for (int j = down; j >= up; j--){
+                    path[step++] = matrix[j][left];
+                }
+                left++;
+            }
+        }
+    return path;
     }
 
     /*
@@ -89,10 +141,35 @@ public class MainExercises
         If you're familiar with Lists and ArrayLists, you can also edit the method's
         body to use them instead of arrays.
     */
+    //Helper method
+    private void makePartitions(int remain, int max, List<Integer> current, List<int[]> result){
+        if (remain == 0){
+            int[] arr = new int[current.size()];
+            for (int i = 0; i < current.size(); i++){
+                arr[i] = current.get(i);
+            }
+            result.add(arr);
+            return;
+        }
+
+        for(int i = Math.min(max, remain); i >= 1; i--){
+            current.add(i);
+            makePartitions(remain - i, i, current, result);
+            current.remove(current.size() - 1);
+        }
+}
 
     public int[][] intPartitions(int n) {
-        // todo
-        return null;
+        List<int[]> result = new ArrayList<>();
+        List<Integer> current = new ArrayList<>();
+
+        makePartitions(n, n, current, result);
+
+        int[][] output = new int[result.size()][];
+        for (int i = 0; i < result.size(); i++){
+            output[i] = result.get(i);
+        }
+        return output;
     }