content: package codingquestions.leetcode;
  
  import java.util.List;
  
  /**
   * 2859. Sum of Values at Indices With K Set Bits
   * Solved
   * Easy
   * Topics
   * Companies
   * Hint
   * You are given a 0-indexed integer array nums and an integer k.
   * <p>
   * Return an integer that denotes the sum of elements in nums whose corresponding indices have exactly k set bits in their binary representation.
   * <p>
   * The set bits in an integer are the 1's present when it is written in binary.
   * <p>
   * For example, the binary representation of 21 is 10101, which has 3 set bits.
   * <p>
   * <p>
   * Example 1:
   * <p>
   * Input: nums = [5,10,1,5,2], k = 1
   * Output: 13
   * Explanation: The binary representation of the indices are:
   * 0 = 0002
   * 1 = 0012
   * 2 = 0102
   * 3 = 0112
   * 4 = 1002
   * 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.
   * Example 2:
   * <p>
   * Input: nums = [4,3,2,1], k = 2
   * Output: 1
   * Explanation: The binary representation of the indices are:
   * 0 = 002
   * 1 = 012
   * 2 = 102
   * 3 = 112
   * Only index 3 has k = 2 set bits in its binary representation.
   * Hence, the answer is nums[3] = 1.
   * <p>
   * <p>
   * Constraints:
   * <p>
   * 1 <= nums.length <= 1000
   * 1 <= nums[i] <= 105
   * 0 <= k <= 10
   */
  public class SumofValuesatIndicesWithKSetBits {
  
      public int sumIndicesWithKSetBits(List<Integer> nums, int k) {
  
          int sum = 0;
          for (int i = 0; i < nums.size(); i++) {
              //approach 1
              int a = getcount(i);
              if (a == k) sum += nums.get(i);
              //approach 2
              if (Integer.bitCount(i) == k) sum += nums.get(i);
          }
          return sum;
      }
  
      public int getcount(int i) {
  
          int count = 0;
          while (i > 0) {
              count += i % 2;
              i = i / 2;
          }
  
          return count;
      }
  }