Number Of Sub-arrays With Odd Sum In Array
Count subarrays with odd sum using prefix sums & parity tracking. For each index, add count of opposite parity prefix sums to result. Update counts & take modulo 10^9 + 7 for large inputs.
1524. Number of Sub-arrays With Odd Sum Difficulty: Medium Topics: Array, Math, Dynamic Programming, Prefix Sum Given an array of integers arr, return the number of subarrays with an odd sum. Since the answer can be very large, return it modulo 109 + 7. Example 1: Input: arr = [1,3,5] Output: 4 Explanation: All subarrays are [[1],[1,3],[1,3,5],[3],[3,5],[5]] All sub-arrays sum are [1,4,9,3,8,5]. Odd sums are [1,9,3,5] so the answer is 4. Example 2: Input: arr = [2,4,6] Output: 0 Explanation: All subarrays are [[2],[2,4],[2,4,6],[4],[4,6],[6]] All sub-arrays sum are [2,6,12,4,10,6]. All...