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leetcode/problem/number-of-sub-arrays-with-odd-sum.html

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+<p>Given an array of integers <code>arr</code>, return <em>the number of subarrays with an <strong>odd</strong> sum</em>.</p>
+
+<p>Since the answer can be very large, return it modulo <code>10<sup>9</sup> + 7</code>.</p>
+
+<p>&nbsp;</p>
+<p><strong>Example 1:</strong></p>
+
+<pre>
+<strong>Input:</strong> arr = [1,3,5]
+<strong>Output:</strong> 4
+<strong>Explanation:</strong> 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.
+</pre>
+
+<p><strong>Example 2:</strong></p>
+
+<pre>
+<strong>Input:</strong> arr = [2,4,6]
+<strong>Output:</strong> 0
+<strong>Explanation:</strong> 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.
+</pre>
+
+<p><strong>Example 3:</strong></p>
+
+<pre>
+<strong>Input:</strong> arr = [1,2,3,4,5,6,7]
+<strong>Output:</strong> 16
+</pre>
+
+<p>&nbsp;</p>
+<p><strong>Constraints:</strong></p>
+
+<ul>
+	<li><code>1 &lt;= arr.length &lt;= 10<sup>5</sup></code></li>
+	<li><code>1 &lt;= arr[i] &lt;= 100</code></li>
+</ul>