# 0042.Trapping-Rain-Water

## Description

Given two binary strings, return their sum \(also a binary string\).

The input strings are both **non-empty** and contains only characters `1` or `0`.

**Example 1:**

```text
Input: a = "11", b = "1"
Output: "100"
```

**Example 2:**

```text
Input: a = "1010", b = "1011"
Output: "10101"
```

**Tags:** Math, String

## 题意

> 给你两个二进制串，求其和的二进制串。

## 题解

### 思路1

> 按照小学算数那么来做，用 `carry` 表示进位，从后往前算，依次往前，每算出一位就插入到最前面即可，直到把两个二进制串都遍历完即可。

```go

```

### 思路2

> 思路2 \`\`\`go

\`\`\`

## 结语

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