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371. Sum of Two Integers 👎

  • Time: $O(32)$
  • Space: $O(1)$
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class Solution {
 public:
  int getSum(unsigned a, unsigned b) {
    while (b > 0) {                  // Still have carry bits.
      const unsigned carry = a & b;  // Record the carry bits.
      a ^= b;  // ^ works like + without handling carry bits.
      b = carry << 1;
    }
    return a;
  }
};

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class Solution {
  public int getSum(int a, int b) {
    while (b != 0) {           // Still have carry bits.
      final int carry = a & b; // Record the carry bits.
      a ^= b;                  // ^ works like + without handling carry bits.
      b = carry << 1;
    }
    return a;
  }
}

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class Solution:
  def getSum(self, a: int, b: int) -> int:
    mask = 0xFFFFFFFF
    kMax = 2000

    while b != 0:
      a, b = (a ^ b) & mask, ((a & b) << 1) & mask

    return a if a < kMax else ~(a ^ mask)