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Sum of Two Integers⚓︎

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Description⚓︎

Given two integers a and b, return the sum of the two integers without using the operators + and -.

Example 1:

  • Input: a = 1, b = 2
  • Output: 3

Example 2:

  • Input: a = 2, b = 3
  • Output: 5

Constraints:

  • -1000 <= a, b <= 1000

Solution⚓︎

See reference 1 and reference 2 (Chinese).

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class Solution {
public:
    int getSum(int a, int b) {
        if (!b) return a;
        int sum = a ^ b, carry = (unsigned)(a & b) << 1;
        return getSum(sum, carry);
    }
};

Without recursion:

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class Solution {
public:
    int getSum(int a, int b) {
        while (b) {
            unsigned carry = (unsigned)(a & b) << 1;
            a = a ^ b;
            b = carry;
        }
        return a;
    }
};