| | | 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.FindTheStudentThatWillReplaceTheChalk; |
| | | 13 | | |
| | | 14 | | /// <inheritdoc /> |
| | | 15 | | public class FindTheStudentThatWillReplaceTheChalkBinarySearch : IFindTheStudentThatWillReplaceTheChalk |
| | | 16 | | { |
| | | 17 | | /// <summary> |
| | | 18 | | /// Time complexity - O(n) |
| | | 19 | | /// Space complexity - O(n) |
| | | 20 | | /// </summary> |
| | | 21 | | /// <param name="chalk"></param> |
| | | 22 | | /// <param name="k"></param> |
| | | 23 | | /// <returns></returns> |
| | | 24 | | public int ChalkReplacer(int[] chalk, int k) |
| | 8 | 25 | | { |
| | 8 | 26 | | var prefixSum = new long[chalk.Length]; |
| | | 27 | | |
| | 8 | 28 | | prefixSum[0] = chalk[0]; |
| | | 29 | | |
| | 182 | 30 | | for (var i = 1; i < prefixSum.Length; i++) |
| | 83 | 31 | | { |
| | 83 | 32 | | prefixSum[i] = prefixSum[i - 1] + chalk[i]; |
| | 83 | 33 | | } |
| | | 34 | | |
| | 8 | 35 | | return GetStudentIndex(prefixSum, k % prefixSum[^1]); |
| | 8 | 36 | | } |
| | | 37 | | |
| | | 38 | | private static int GetStudentIndex(long[] prefixSum, long remainder) |
| | 8 | 39 | | { |
| | 8 | 40 | | var left = 0; |
| | 8 | 41 | | var right = prefixSum.Length - 1; |
| | | 42 | | |
| | 31 | 43 | | while (left < right) |
| | 23 | 44 | | { |
| | 23 | 45 | | var mid = left + ((right - left) / 2); |
| | | 46 | | |
| | 23 | 47 | | if (prefixSum[mid] <= remainder) |
| | 6 | 48 | | { |
| | 6 | 49 | | left = mid + 1; |
| | 6 | 50 | | } |
| | | 51 | | else |
| | 17 | 52 | | { |
| | 17 | 53 | | right = mid; |
| | 17 | 54 | | } |
| | 23 | 55 | | } |
| | | 56 | | |
| | 8 | 57 | | return right; |
| | 8 | 58 | | } |
| | | 59 | | } |