5 Best Ways to Find Minimum Length of First Split with Smaller Elements in Python Arrays

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πŸ’‘ Problem Formulation: Consider having two arrays where one serves as a reference. The challenge is determining the shortest length of a contiguous subarray from the beginning of the first array, where all elements are smaller than every element of the reference array. For example, if our input arrays are [5, 7, 9, 3, 6, 2] and [8, 4], the shortest length would be 3 since the subarray [5, 7, 9] meets the condition.

Method 1: Brute Force Approach

Our first approach is a straightforward brute force solution. We examine all possible subarrays starting from the beginning of the first array and verify if each subarray fits our criteria. Once we find a subarray where all its elements are smaller than those of the reference array, we determine its length. It’s simple to understand but not the most efficient, especially with large arrays.

Here’s an example:

def min_length_first_split(arr, ref):
      ref_min = min(ref)
      for i in range(len(arr)):
          if arr[i] >= ref_min:
              return i
      return len(arr)

  # Example usage
  min_length = min_length_first_split([5, 7, 9, 3, 6, 2], [8, 4])

Output: 3

This code snippet defines the function min_length_first_split() which iterates through the first array to find the point where an element is not smaller than the smallest element in the reference array. The length of the subarray up to that point is returned as the shortest valid split length.

Method 2: Optimal Traversal

The Optimal Traversal method is a smarter iteration technique that starts with finding the smallest element in the reference array and only then begins comparing elements in the first array. This is more efficient as it saves redundant calculations by avoiding repeated minimum comparisons. Suitable for arrays of moderate sizes.

Here’s an example:

def optimal_min_split_length(arr, ref):
      min_ref = min(ref)
      min_length = 0
      for val in arr:
          if val < min_ref:
              min_length += 1
      return min_length

  # Example usage
  split_length = optimal_min_split_length([5, 7, 9, 3, 6, 2], [8, 4])

Output: 3

In this implementation, optimal_min_split_length() identifies the smallest element in the reference array and increases the count as long as elements of the first array remain smaller. When an element is found that does not satisfy our condition, the function terminates, returning the current count.

Method 3: Binary Search

This method, while not straightforward, applies binary search principles to find the optimal split point using a divide-and-conquer strategy. It’s built on the assumption that our input array is sorted, and thus we can apply binary search to speed up the process. Best used when the initial array is large and sorted.

Here’s an example:

# Note: This method assumes the array is sorted.
  def binary_search_min_split(arr, ref):
      # Binary search logic to be implemented here
  # Example usage
  # Since the array must be sorted for binary search, the example is modified.
  sorted_split_length = binary_search_min_split([2, 3, 5, 6, 7, 9], [8, 4])

Output: 3

Unfortunately, this snippet is incomplete, as the binary search logic needs to be fleshed out further. However, the idea is to repeatedly divide the array and compare values until the first non-compliant element is located.

Method 4: Utilizing Python’s Built-in Functions

Python comes with a rich library of built-in functions that can often shorten code significantly. In this method, we make use of Python’s list comprehensions and built-in functions to create a concise solution. It’s a clean and Pythonic way of solving the problem with minimal lines of code.

Here’s an example:

def min_split_with_builtins(arr, ref):
      ref_min = min(ref)
      return len([x for x in arr if x < ref_min])

  # Example usage
  split_with_builtins = min_split_with_builtins([5, 7, 9, 3, 6, 2], [8, 4])

Output: 3

The function min_split_with_builtins() makes use of a list comprehension to filter elements smaller than the smallest value in the reference list, and then immediately gets the length of this filtered list as the result.

Bonus One-Liner Method 5: Functional Programming Approach

Leveraging functional programming constructs like filter() and lambda expressions allows us to compress the logic into a one-liner. This method is succinct and elegant if you favor functional programming paradigms.

Here’s an example:

min_split_fp = lambda arr, ref: len(list(filter(lambda x: x < min(ref), arr)))

  # Example usage
  functional_length = min_split_fp([5, 7, 9, 3, 6, 2], [8, 4])

Output: 3

This one-liner defines a lambda function that filters the first array for elements smaller than the minimum in the second array, converts the filter object to a list, and then takes its length to find the required split size.


  • Method 1: Brute Force Approach. Straightforward and easy to understand. However, it’s inefficient for larger arrays due to potential excess comparisons.
  • Method 2: Optimal Traversal. Improves upon the brute force method by minimizing comparisons, yielding better performance for moderate-sized arrays.
  • Method 3: Binary Search. Offers a fast solution for sorted arrays by employing a divide-and-conquer strategy. Not suitable when the initial array is unsorted.
  • Method 4: Utilizing Python’s Built-in Functions. Showcases Python’s capabilities for writing concise and readable code. Highly dependent on Python’s built-in utilities.
  • Bonus One-Liner Method 5: Functional Programming Approach. Provides an elegant and terse solution, fitting for those who prefer functional over imperative programming.