| | | 1 | | // -------------------------------------------------------------------------------- |
| | | 2 | | // Copyright (C) 2026 Eugene Eremeev (also known as Yevhenii Yeriemeieiv). |
| | | 3 | | // All Rights Reserved. |
| | | 4 | | // -------------------------------------------------------------------------------- |
| | | 5 | | // This software is the confidential and proprietary information of Eugene Eremeev |
| | | 6 | | // (also known as Yevhenii Yeriemeieiv) ("Confidential Information"). You shall not |
| | | 7 | | // disclose such Confidential Information and shall use it only in accordance with |
| | | 8 | | // the terms of the license agreement you entered into with Eugene Eremeev (also |
| | | 9 | | // known as Yevhenii Yeriemeieiv). |
| | | 10 | | // -------------------------------------------------------------------------------- |
| | | 11 | | |
| | | 12 | | namespace LeetCode.Algorithms.ValidTriangleNumber; |
| | | 13 | | |
| | | 14 | | /// <inheritdoc /> |
| | | 15 | | public sealed class ValidTriangleNumberSortingTwoPointers : IValidTriangleNumber |
| | | 16 | | { |
| | | 17 | | /// <summary> |
| | | 18 | | /// Time complexity - O(n^2) |
| | | 19 | | /// Space complexity - O(1) |
| | | 20 | | /// </summary> |
| | | 21 | | /// <param name="nums"></param> |
| | | 22 | | /// <returns></returns> |
| | | 23 | | public int TriangleNumber(int[] nums) |
| | 2 | 24 | | { |
| | 2 | 25 | | var numsLength = nums.Length; |
| | | 26 | | |
| | 2 | 27 | | if (numsLength < 3) |
| | 0 | 28 | | { |
| | 0 | 29 | | return 0; |
| | | 30 | | } |
| | | 31 | | |
| | 2 | 32 | | Array.Sort(nums); |
| | | 33 | | |
| | 2 | 34 | | var count = 0; |
| | | 35 | | |
| | 12 | 36 | | for (var cIndex = numsLength - 1; cIndex > 1; cIndex--) |
| | 4 | 37 | | { |
| | 4 | 38 | | var aIndex = 0; |
| | 4 | 39 | | var bIndex = cIndex - 1; |
| | | 40 | | |
| | 10 | 41 | | while (aIndex < bIndex) |
| | 6 | 42 | | { |
| | 6 | 43 | | var a = nums[aIndex]; |
| | 6 | 44 | | var b = nums[bIndex]; |
| | 6 | 45 | | var c = nums[cIndex]; |
| | | 46 | | |
| | 6 | 47 | | if (a + b > c) |
| | 5 | 48 | | { |
| | 5 | 49 | | count += bIndex - aIndex; |
| | | 50 | | |
| | 5 | 51 | | bIndex--; |
| | 5 | 52 | | } |
| | | 53 | | else |
| | 1 | 54 | | { |
| | 1 | 55 | | aIndex++; |
| | 1 | 56 | | } |
| | 6 | 57 | | } |
| | 4 | 58 | | } |
| | | 59 | | |
| | 2 | 60 | | return count; |
| | 2 | 61 | | } |
| | | 62 | | } |