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Sum of Two Integers

MediumBit Manipulation

Compute the sum of two integers without using the + or - operators.

Open problem
Constraints
  • -1000 <= a, b <= 1000

Bitwise add with carry

Time O(1) (fixed 32 bits)Space O(1)

The XOR of two numbers is the sum without carries; the AND shifted left is the carry. Repeat until there is no carry left.

int getSum(int a, int b) {
    while (b != 0) {
        unsigned carry = (unsigned)(a & b) << 1;
        a = a ^ b;
        b = carry;
    }
    return a;
}