> For the complete documentation index, see [llms.txt](https://liuyang89116.gitbook.io/my-leetcode-book/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://liuyang89116.gitbook.io/my-leetcode-book/post_chapter_2_math/bit-manipulation/problem-371-sum-of-two-integers.md).

# Problem 371: Sum of Two Integers

> <https://leetcode.com/problems/sum-of-two-integers/>

## 思路

> <https://discuss.leetcode.com/topic/49771/java-simple-easy-understand-solution-with-explanation>
>
> <https://discuss.leetcode.com/topic/50315/a-summary-how-to-use-bit-manipulation-to-solve-problems-easily-and-efficiently>

这两篇对于 bit manipulation 的总结非常好！

* 首先用 `a & b` 来得到进位，并且循环的退出条件是什么时候没有进位了，什么时候就退出。
* 然后用 `a ^ b` 来得到不同的 bit
* 最后把 carrier shift，以此类推

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

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

        return a;
    }
}
```