FlattenArray done

Author: Ram Patra

src/main/java/com/rampatra/arrays/FlattenArray.java

@@ -0,0 +1,39 @@
+package com.rampatra.arrays;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class FlattenArray {
+
+    /**
+     * Given a nested array like [[1, 2], 3, [4]], return an array like [1, 2, 3, 4, 5].
+     *
+     * @param nestedArray an Object array
+     * @return a list of all elements in the nestedArray but all at the same level
+     */
+    private static List<Integer> flattenArray(Object[] nestedArray) {
+        if (nestedArray == null || nestedArray.length == 0) return new ArrayList<>();
+
+        List<Integer> flattenedArray = new ArrayList<>();
+
+        for (Object obj : nestedArray) {
+            if (obj instanceof Object[]) {
+                flattenedArray.addAll(flattenArray((Object[]) obj));
+            } else if (obj instanceof Integer) {
+                flattenedArray.add((Integer) obj);
+            }
+        }
+
+        return flattenedArray;
+    }
+
+    public static void main(String[] args) {
+        System.out.println(flattenArray(null));
+        System.out.println(flattenArray(new Object[]{null}));
+        System.out.println(flattenArray(new Object[]{new Object[]{}}));
+        System.out.println(flattenArray(new Object[]{new Object[]{1, 2}}));
+        System.out.println(flattenArray(new Object[]{1, 2, new Object[]{4, 5}, 6}));
+        System.out.println(flattenArray(new Object[]{new Object[]{4, 5}, 1, 2, 6}));
+        System.out.println(flattenArray(new Object[]{1, 2, 6, new Object[]{4, 5}}));
+    }
+}