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The idea behind this approach is to use recursion to flatten the array up to the specified depth n. If the current depth is less than n, we continue flattening; otherwise, we do not flatten further. We leverage recursive calls to process each element and manage the depth level.
Time Complexity: O(m) where m is the total number of elements in the array considering all levels.
Space Complexity: O(m) due to recursive stack space and storage of flattened elements.
using System.Collections.Generic;
class FlattenArray {
public static List<int> Flatten(List<object> arr, int maxDepth) {
List<int> result = new List<int>();
FlattenHelper(arr, maxDepth, 0, result);
return result;
}
private static void FlattenHelper(List<object> arr, int maxDepth, int currentDepth, List<int> result) {
foreach (var element in arr) {
if (element is List<object> sublist) {
if (currentDepth < maxDepth)
FlattenHelper(sublist, maxDepth, currentDepth + 1, result);
else
result.AddRange((List<int>)sublist);
} else {
result.Add((int)element);
}
}
}
static void Main() {
var arr = new List<object> { 1, 2, new List<object> { 3, 4 }, 5 };
var flattened = Flatten(arr, 1);
Console.WriteLine(string.Join(", ", flattened));
}
}This C# solution involves a recursive method FlattenHelper, which processes a nested List structure. It checks objects for List types and regulates depth accordingly. Upon encountering integers, it accumulates them into result, signalling depth compliance.
This technique leverages a stack data structure to simulate recursion iteratively. By using an explicit stack, we can iteratively flatten the array, taking control of the depth level without using the actual recursive calls within the stack frames.
Time Complexity: O(m), iterating through each array element.
Space Complexity: O(m) due to storage in stack elements.
1def flatten_array(arr, n):
2 stack = [(arr, 0)]
3 result = []
4
5 while stack:
6 curr, depth = stack.pop()
7 i = 0
8 while i < len(curr):
9 if isinstance(curr[i], list):
10 if depth < n:
11 stack.append((curr, i + 1))
12 stack.append((curr[i], depth + 1))
13 break
14 else:
15 result.extend(curr[i])
16 else:
17 result.append(curr[i])
18 i += 1
19 return result
20
21# Example usage:
22arr = [1, [2, [3, 4], 5], 6, [7, 8]]
23print(flatten_array(arr, 1)) Python’s stack-based solution iterates over the input list using a manual stack. Given tuples holding both the current list and index, flatten_array() evaluates depth to determine their inclusion, breaking into subarrays where appropriate.