| | | 1 | | // -------------------------------------------------------------------------------- |
| | | 2 | | // Copyright (C) 2025 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.FirstMissingPositive; |
| | | 13 | | |
| | | 14 | | /// <inheritdoc /> |
| | | 15 | | public class FirstMissingPositiveIterative : IFirstMissingPositive |
| | | 16 | | { |
| | | 17 | | /// <summary> |
| | | 18 | | /// Time complexity - O(n) |
| | | 19 | | /// Space complexity - O(1) |
| | | 20 | | /// </summary> |
| | | 21 | | /// <param name="nums"></param> |
| | | 22 | | /// <returns></returns> |
| | | 23 | | public int FirstMissingPositive(int[] nums) |
| | 12 | 24 | | { |
| | 12 | 25 | | var n = nums.Length; |
| | | 26 | | |
| | 100 | 27 | | for (var i = 0; i < n; ++i) |
| | 38 | 28 | | { |
| | 38 | 29 | | if (nums[i] <= 0 || nums[i] > n) |
| | 16 | 30 | | { |
| | 16 | 31 | | nums[i] = n + 1; |
| | 16 | 32 | | } |
| | 38 | 33 | | } |
| | | 34 | | |
| | 100 | 35 | | for (var i = 0; i < n; ++i) |
| | 38 | 36 | | { |
| | 38 | 37 | | var num = Math.Abs(nums[i]); |
| | | 38 | | |
| | 38 | 39 | | if (num > n) |
| | 16 | 40 | | { |
| | 16 | 41 | | continue; |
| | | 42 | | } |
| | | 43 | | |
| | 22 | 44 | | num--; |
| | | 45 | | |
| | 22 | 46 | | if (nums[num] > 0) |
| | 19 | 47 | | { |
| | 19 | 48 | | nums[num] = -1 * nums[num]; |
| | 19 | 49 | | } |
| | 22 | 50 | | } |
| | | 51 | | |
| | 54 | 52 | | for (var i = 0; i < n; ++i) |
| | 23 | 53 | | { |
| | 23 | 54 | | if (nums[i] >= 0) |
| | 8 | 55 | | { |
| | 8 | 56 | | return i + 1; |
| | | 57 | | } |
| | 15 | 58 | | } |
| | | 59 | | |
| | 4 | 60 | | return n + 1; |
| | 12 | 61 | | } |
| | | 62 | | } |