371. Sum of Two Integers

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Problem

Calculate the sum of two integers a and b, but you are not allowed to use the operator + and -.

Example 1:

Input: a = 1, b = 2
Output: 3

Example 2:

Input: a = -2, b = 3
Output: 1

Code

• a + b 相当于 a ^ b 如果不考虑进位的计算
• 使用 int carry = a & b, 可以计算出当前 a 和 b 的进位

class Solution {
    public int getSum(int a, int b) {
        if(a == 0) return b;
        if(b == 0) return a;

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

        return a;
    }
}