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3064. Guess the Number Using Bitwise Questions I

  • Time: $O(30) = O(1)$
  • Space: $O(1)$
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/**
 * Definition of commonSetBits API.
 * int commonSetBits(int num);
 */

class Solution {
 public:
  int findNumber() {
    constexpr int kMaxBit = 30;
    int ans = 0;
    for (int i = 0; i <= kMaxBit; ++i)
      if (commonSetBits(1 << i) == 1)
        ans |= 1 << i;
    return ans;
  }
};

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/**
 * Definition of commonSetBits API (defined in the parent class Problem).
 * int commonSetBits(int num);
 */

public class Solution extends Problem {
  public int findNumber() {
    final int MAX_BIT = 30;
    int ans = 0;
    for (int i = 0; i <= MAX_BIT; ++i)
      if (commonSetBits(1 << i) == 1)
        ans |= 1 << i;
    return ans;
  }
}

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# Definition of commonSetBits API.
# def commonSetBits(num: int) -> int:

class Solution:
  def findNumber(self) -> int:
    return sum(1 << i for i in range(31)
               if commonSetBits(1 << i) == 1)