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# 1524. Number of Sub-arrays With Odd Sum

<https://leetcode.com/problems/number-of-sub-arrays-with-odd-sum>

## Description

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 sub-arrays have even sum and the answer is 0.
```

**Example 3:**

```
**Input:** arr = [1,2,3,4,5,6,7]
**Output:** 16
```

**Constraints:**

* `1 <= arr.length <= 105`
* `1 <= arr[i] <= 100`

## ac

```java
```