Java||BFS
Intuition\nThe goal of this problem is to flatten a nested array with a specified depth. We can achieve this by using a breadth-first approach where we process 
# Intuition\nThe goal of this problem is to flatten a nested array with a specified depth. We can achieve this by using a breadth-first approach where we process the array elements level by level up to the given depth.\n\n# Approach\n1. We start by initializing a queue to hold the elements of the array.\n2. We iterate through each depth level while reducing the depth count.\n3. For each level, we process the current number of elements in the queue (since the queue size may change as we add elements).\n4. If an element in the queue is a list, we convert it to a subarray and add its individual elements to the queue.\n5. If an element is not a list, we add it back to the queue.\n6. Repeat the above steps for the specified depth.\n7. After processing all levels, the queue contains the flattened array with the specified depth.\n\n# Complexity\n- Time complexity: O(N * D), where N is the total number of elements in the input array and D is the specified depth.\n- Space complexity: O(N), where N is the total number of elements in the input array.\n\n# Further improvements\nIn our current approach, we are processing each element as we reduce the depth. However, it\'s necessary to only process elements that are lists each time we delve deeper.\n\n# Code\n```java\nimport java.util.ArrayList;\nimport java.util.Arrays;\nimport java.util.LinkedList;\nimport java.util.List;\nimport java.util.Queue;\n\npublic class FlattenArray {\n    public static List<Object> flatten(Object[] arr, int depth) {\n        Queue<Object> queue = new LinkedList<>();\n        queue.addAll(Arrays.asList(arr));\n\n        while (depth > 0) {\n            int size = queue.size();\n            for (int i = 0; i < size; i++) {\n                Object item = queue.poll();\n                if (item instanceof List<?>) {\n                    List<Object> subArray = new ArrayList<Object>((List<?>) item);\n                    queue.addAll(subArray);\n                } else {\n                    queue.add(item);\n                }\n            }\n            depth--;\n        }\n\n        return new ArrayList<Object>(queue);\n    }\n\n    public static void main(String[] args) {\n        Object[] arr = new Object[]{\n            1, 2, 3,\n            Arrays.asList(4, 5, 6),\n            Arrays.asList(\n                7, 8,\n                Arrays.asList(9, 10, 11),\n                12\n            ),\n            Arrays.asList(13, 14, 15)\n        };\n\n        List<Object> flattened = flatten(arr, 1);\n        System.out.println(flattened);\n    }\n}\n\n
['Breadth-First Search', 'Java']