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260. Single Number III 👍

  • Time: $O(n)$
  • Space: $O(1)$
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class Solution {
 public:
  vector<int> singleNumber(vector<int>& nums) {
    const int xors = accumulate(nums.begin(), nums.end(), 0, bit_xor<>());
    const int lowbit = xors & -xors;
    vector<int> ans(2);

    // Seperate `nums` into two groups by `lowbit`.
    for (const int num : nums)
      if (num & lowbit)
        ans[0] ^= num;
      else
        ans[1] ^= num;

    return ans;
  }
};

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class Solution {
  public int[] singleNumber(int[] nums) {
    final int xors = Arrays.stream(nums).reduce((a, b) -> a ^ b).getAsInt();
    final int lowbit = xors & -xors;
    int[] ans = new int[2];

    // Seperate `nums` into two groups by `lowbit`.
    for (final int num : nums)
      if ((num & lowbit) > 0)
        ans[0] ^= num;
      else
        ans[1] ^= num;

    return ans;
  }
}

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class Solution:
  def singleNumber(self, nums: List[int]) -> List[int]:
    xors = functools.reduce(operator.xor, nums)
    lowbit = xors & -xors
    ans = [0, 0]

    # Seperate `nums` into two groups by `lowbit`.
    for num in nums:
      if num & lowbit:
        ans[0] ^= num
      else:
        ans[1] ^= num

    return ans