For a given list of integers and integer `K`, find the number of non-empty subsets `S` such that `min(S) + max(S) <= K`.\n\n**Example 1:**\n```\nnums = [2, 4, 5, 7]\nk = 8\nOutput: 5\nExplanation: [2], [4], [2, 4], [2, 4, 5], [2, 5]\n```\n\n**Example 2:**\n```\nnums = [1, 4, 3, 2]\nk = 8\nOutput: 15\nExplanation: 16 (2^4) - 1 (empty set) = 15\n```\n\n**Example 3:**\n```\nnums = [2, 4, 2, 5, 7]\nk = 10\nOutput: 27\nExplanation: 31 (2^5 - 1) - 4 ([7], [5, 7], [4, 5, 7], [4, 7]) = 27\n```\n\nExpected `O(n^2)` time solution or better.\n\n<details> \n  <summary>My Java solution</summary>\n\n https://leetcode.com/playground/hDWHqqUX\nTime complexity: `O(nlogn)`.\nSpace complexity: `O(1)`.\n</details>

For a given list of integers and integer K, find the number of non-empty subsets S such that min(S) + max(S) <= K.\n\nExample 1:\n\nnums = [2, 4, 5, 7]\nk = 8\n