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leetcode/problem/sum-of-values-at-indices-with-k-set-bits.html

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+<p>You are given a <strong>0-indexed</strong> integer array <code>nums</code> and an integer <code>k</code>.</p>
+
+<p>Return <em>an integer that denotes the <strong>sum</strong> of elements in </em><code>nums</code><em> whose corresponding <strong>indices</strong> have <strong>exactly</strong> </em><code>k</code><em> set bits in their binary representation.</em></p>
+
+<p>The <strong>set bits</strong> in an integer are the <code>1</code>&#39;s present when it is written in binary.</p>
+
+<ul>
+	<li>For example, the binary representation of <code>21</code> is <code>10101</code>, which has <code>3</code> set bits.</li>
+</ul>
+
+<p>&nbsp;</p>
+<p><strong class="example">Example 1:</strong></p>
+
+<pre>
+<strong>Input:</strong> nums = [5,10,1,5,2], k = 1
+<strong>Output:</strong> 13
+<strong>Explanation:</strong> The binary representation of the indices are: 
+0 = 000<sub>2</sub>
+1 = 001<sub>2</sub>
+2 = 010<sub>2</sub>
+3 = 011<sub>2</sub>
+4 = 100<sub>2 
+</sub>Indices 1, 2, and 4 have k = 1 set bits in their binary representation.
+Hence, the answer is nums[1] + nums[2] + nums[4] = 13.</pre>
+
+<p><strong class="example">Example 2:</strong></p>
+
+<pre>
+<strong>Input:</strong> nums = [4,3,2,1], k = 2
+<strong>Output:</strong> 1
+<strong>Explanation:</strong> The binary representation of the indices are:
+0 = 00<sub>2</sub>
+1 = 01<sub>2</sub>
+2 = 10<sub>2</sub>
+3 = 11<sub>2
+</sub>Only index 3 has k = 2 set bits in its binary representation.
+Hence, the answer is nums[3] = 1.
+</pre>
+
+<p>&nbsp;</p>
+<p><strong>Constraints:</strong></p>
+
+<ul>
+	<li><code>1 &lt;= nums.length &lt;= 1000</code></li>
+	<li><code>1 &lt;= nums[i] &lt;= 10<sup>5</sup></code></li>
+	<li><code>0 &lt;= k &lt;= 10</code></li>
+</ul>