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Find the Kth Smallest Element in a List

Certification: Intermediate Level Accuracy: 90.91% Submissions: 11 Points: 5

Write a Python function to find the Kth smallest element in a given list of integers.

Example 1
    
  
  • Input: nums = [7, 10, 4, 3, 20, 15], K = 3
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  • Output: 7
    • 
  
  • Explanation: 
      
    
    • Step 1: Sort the list [7, 10, 4, 3, 20, 15] in ascending order: [3, 4, 7, 10, 15, 20].
      • 
    
    • Step 2: Find the element at index K-1 (since indexing starts at 0): element at index 2 is 7.
      • 
    
    • Step 3: Return 7 as the 3rd smallest element.
      • 
  
    •
Example 2
    
  
  • Input: nums = [1, 2, 3, 4, 5], K = 1
    • 
  
  • Output: 1
    • 
  
  • Explanation: 
      
    
    • Step 1: Sort the list [1, 2, 3, 4, 5] in ascending order: [1, 2, 3, 4, 5].
      • 
    
    • Step 2: Find the element at index K-1 (since indexing starts at 0): element at index 0 is 1.
      • 
    
    • Step 3: Return 1 as the 1st smallest element.
      • 
  
    •
Constraints
    
  
  • 1 <= len(list) <= 10^5
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  • 1 <= K <= len(list)
    • 
  
  • -10^9 <= list[i] <= 10^9
    • 
  
  • Time Complexity: O(n log n) or better
    • 
  
  • Space Complexity: O(n)
    •
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Hint
Solution

Solution Hints

    
  
  • Sort the list and return the Kth element: sorted_list = sorted(lst); return sorted_list[K-1]
    • 
  
  • Use a min-heap to efficiently find the Kth smallest element: import heapq; heapq.nsmallest(K, lst)[-1]
    • 
  
  • Handle edge cases where K is out of bounds or the list is empty.
    •

Steps to solve by this approach:

 Step 1: Check for edge cases: empty list or invalid k value

 Step 2: Sort the input list in ascending order

 Step 3: Access the (k-1)th element in the sorted list

 Step 4: Return the element at index (k-1)

 Step 5: This works because after sorting, the kth smallest element is at index (k-1)

 Step 6: Handle invalid inputs by returning None for impossible cases

 Step 7: Return the kth smallest element found in the sorted list

Submitted Code :