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# 0389. Find the Difference

<https://leetcode.com/problems/find-the-difference>

## Description

You are given two strings `s` and `t`.

String `t` is generated by random shuffling string `s` and then add one more letter at a random position.

Return the letter that was added to `t`.

**Example 1:**

```
**Input:** s = "abcd", t = "abcde"
**Output:** "e"
**Explanation:** 'e' is the letter that was added.
```

**Example 2:**

```
**Input:** s = "", t = "y"
**Output:** "y"
```

**Example 3:**

```
**Input:** s = "a", t = "aa"
**Output:** "a"
```

**Example 4:**

```
**Input:** s = "ae", t = "aea"
**Output:** "a"
```

**Constraints:**

* `0 <= s.length <= 1000`
* `t.length == s.length + 1`
* `s` and `t` consist of lower-case English letters.

## ac

```java
```