leetcode 371. Sum of Two Integers

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题目

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

Example

Given a = 1 and b = 2, return 3.

解法一

对于位运算的加法而言。a^b结果为无进位加法，而a&b结果则为每位的进位结果。进位数要左移1位相加，当a&b == 0的时候表示无进位，即加法结束。

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