> For the complete documentation index, see [llms.txt](https://imhuay.gitbook.io/studies/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://imhuay.gitbook.io/studies/algorithms/problems/2022/01/niu-ke-0001-zhong-deng-da-shu-jia-fa.md).

# 大数加法

![last modify](https://img.shields.io/static/v1?label=last%20modify\&message=2022-10-14%2014%3A59%3A33\&color=yellowgreen\&style=flat-square) [![](https://img.shields.io/static/v1?label=\&message=%E4%B8%AD%E7%AD%89\&color=yellow\&style=flat-square)](https://imhuay.gitbook.io/studies/algorithms/problems/2022/01/pages/R5NyOzkn3qAZy7wCx1pS#中等) [![](https://img.shields.io/static/v1?label=\&message=%E7%89%9B%E5%AE%A2\&color=green\&style=flat-square)](https://imhuay.gitbook.io/studies/algorithms/problems/2022/01/pages/R5NyOzkn3qAZy7wCx1pS#牛客) [![](https://img.shields.io/static/v1?label=\&message=%E5%AD%97%E7%AC%A6%E4%B8%B2\&color=blue\&style=flat-square)](https://imhuay.gitbook.io/studies/algorithms/problems/2022/01/pages/R5NyOzkn3qAZy7wCx1pS#字符串) [![](https://img.shields.io/static/v1?label=\&message=%E6%A8%A1%E6%8B%9F\&color=blue\&style=flat-square)](https://imhuay.gitbook.io/studies/algorithms/problems/2022/01/pages/R5NyOzkn3qAZy7wCx1pS#模拟)

**问题简述**

```
以字符串的形式读入两个数字，计算它们的和，以字符串形式返回。
```

> [大数加法\_牛客题霸\_牛客网](https://www.nowcoder.com/practice/11ae12e8c6fe48f883cad618c2e81475)

**思路**

* 把较短的字符串通过补前缀 0 使长度一致，此时只要处理好进位即可；

<details>

<summary><strong>Python</strong></summary>

```python
class Solution:
    def solve(self , s: str, t: str) -> str:
        # write code here
        n, m = len(s), len(t)
        if n < m:  # 确保 n >= m
            s, t = t, s
            n, m = m, n
            
        t = '0' * (n - m) + t  # 补0
        
        ret = ''
        ex = 0  # 进位标志
        for i in range(n - 1, -1, -1):
            r = int(s[i]) + int(t[i]) + ex
            ret = str(r % 10) + ret
            ex = r // 10
            
        if ex:
            ret = '1' + ret
        
        return ret
```

</details>