algoadvance

You are given a list of integers. Implement a function that returns the first element that is neither the minimum nor the maximum in the list. If no such element exists, return -1.

Clarifying Questions

  1. Input Constraints:
    • What is the maximum size of the list?
    • Can the list contain duplicate values?
    • Can the list be empty or contain fewer than three elements?
  2. Output Specifications:
    • If there are multiple valid elements, should we return the first instance or any one of them?
  3. Edge Cases:
    • Lists with all elements being the same.
    • Lists with only two elements.

Strategy

  1. Identify the Minimum and Maximum Elements:
    • Traverse the list to find the minimum and maximum values.
  2. Finding the Non-Min/Max Element:
    • Traverse the list again and find the first element that is neither the minimum nor the maximum.
  3. Edge Cases Handling:
    • If the list has fewer than three elements, immediately return -1 because it is impossible to have an element that is neither min nor max.

Time Complexity

Code

def neither_min_nor_max(nums):
    if len(nums) < 3:
        return -1
    
    min_val = min(nums)
    max_val = max(nums)
    
    for num in nums:
        if num != min_val and num != max_val:
            return num
    
    return -1

Explanation

  1. Edge Case Handling: If the list has fewer than three elements, return -1.
  2. Min and Max Calculation: Use Python’s built-in min and max functions to find the minimum and maximum values of the list.
  3. Finding the Result: Loop through the list again to find and return the first element that is not equal to either the minimum or the maximum value.
  4. Return -1 if Not Found: If no such element exists, return -1.

This solution ensures we efficiently find the required element with linear time complexity.

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