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49 lines
1.2 KiB
HTML
49 lines
1.2 KiB
HTML
<p>Given an array of positive integers <code>arr</code>, return <em>the sum of all possible <strong>odd-length subarrays</strong> of </em><code>arr</code>.</p>
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<p>A <strong>subarray</strong> is a contiguous subsequence of the array.</p>
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<p> </p>
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<p><strong class="example">Example 1:</strong></p>
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<pre>
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<strong>Input:</strong> arr = [1,4,2,5,3]
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<strong>Output:</strong> 58
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<strong>Explanation: </strong>The odd-length subarrays of arr and their sums are:
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[1] = 1
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[4] = 4
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[2] = 2
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[5] = 5
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[3] = 3
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[1,4,2] = 7
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[4,2,5] = 11
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[2,5,3] = 10
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[1,4,2,5,3] = 15
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If we add all these together we get 1 + 4 + 2 + 5 + 3 + 7 + 11 + 10 + 15 = 58</pre>
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<p><strong class="example">Example 2:</strong></p>
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<pre>
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<strong>Input:</strong> arr = [1,2]
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<strong>Output:</strong> 3
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<b>Explanation: </b>There are only 2 subarrays of odd length, [1] and [2]. Their sum is 3.</pre>
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<p><strong class="example">Example 3:</strong></p>
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<pre>
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<strong>Input:</strong> arr = [10,11,12]
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<strong>Output:</strong> 66
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</pre>
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<p> </p>
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<p><strong>Constraints:</strong></p>
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<ul>
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<li><code>1 <= arr.length <= 100</code></li>
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<li><code>1 <= arr[i] <= 1000</code></li>
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</ul>
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<p> </p>
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<p><strong>Follow up:</strong></p>
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<p>Could you solve this problem in O(n) time complexity?</p>
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