| | | 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.NumberOfSubArraysWithOddSum; |
| | | 13 | | |
| | | 14 | | /// <inheritdoc /> |
| | | 15 | | public class NumberOfSubArraysWithOddSumPrefixSum : INumberOfSubArraysWithOddSum |
| | | 16 | | { |
| | | 17 | | private const int Mod = (int)(1e9 + 7); |
| | | 18 | | |
| | | 19 | | /// <summary> |
| | | 20 | | /// Time complexity - O(n) |
| | | 21 | | /// Space complexity - O(1) |
| | | 22 | | /// </summary> |
| | | 23 | | /// <param name="arr"></param> |
| | | 24 | | /// <returns></returns> |
| | | 25 | | public int NumOfSubarrays(int[] arr) |
| | 3 | 26 | | { |
| | 3 | 27 | | var count = 0; |
| | 3 | 28 | | var oddCount = 0; |
| | 3 | 29 | | var evenCount = 1; |
| | 3 | 30 | | var prefixSum = 0; |
| | | 31 | | |
| | 35 | 32 | | foreach (var num in arr) |
| | 13 | 33 | | { |
| | 13 | 34 | | prefixSum += num; |
| | | 35 | | |
| | 13 | 36 | | if (prefixSum % 2 == 0) |
| | 7 | 37 | | { |
| | 7 | 38 | | count += oddCount; |
| | | 39 | | |
| | 7 | 40 | | evenCount++; |
| | 7 | 41 | | } |
| | | 42 | | else |
| | 6 | 43 | | { |
| | 6 | 44 | | count += evenCount; |
| | | 45 | | |
| | 6 | 46 | | oddCount++; |
| | 6 | 47 | | } |
| | | 48 | | |
| | 13 | 49 | | count %= Mod; |
| | 13 | 50 | | } |
| | | 51 | | |
| | 3 | 52 | | return count; |
| | 3 | 53 | | } |
| | | 54 | | } |