国外版

算法题（国外版）/sum-of-subarray-minimums.html

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+<p>Given an array of integers arr, find the sum of <code>min(b)</code>, where <code>b</code> ranges over every (contiguous) subarray of <code>arr</code>. Since the answer may be large, return the answer <strong>modulo</strong> <code>10<sup>9</sup> + 7</code>.</p>
+
+<p>&nbsp;</p>
+<p><strong>Example 1:</strong></p>
+
+<pre>
+<strong>Input:</strong> arr = [3,1,2,4]
+<strong>Output:</strong> 17
+<strong>Explanation:</strong> 
+Subarrays are [3], [1], [2], [4], [3,1], [1,2], [2,4], [3,1,2], [1,2,4], [3,1,2,4]. 
+Minimums are 3, 1, 2, 4, 1, 1, 2, 1, 1, 1.
+Sum is 17.
+</pre>
+
+<p><strong>Example 2:</strong></p>
+
+<pre>
+<strong>Input:</strong> arr = [11,81,94,43,3]
+<strong>Output:</strong> 444
+</pre>
+
+<p>&nbsp;</p>
+<p><strong>Constraints:</strong></p>
+
+<ul>
+	<li><code>1 &lt;= arr.length &lt;= 3 * 10<sup>4</sup></code></li>
+	<li><code>1 &lt;= arr[i] &lt;= 3 * 10<sup>4</sup></code></li>
+</ul>