# 1647. Minimum Deletions to Make Character Frequencies Unique

<https://leetcode.com/problems/minimum-deletions-to-make-character-frequencies-unique>

## Description

A string `s` is called **good** if there are no two different characters in `s` that have the same **frequency**.

Given a string `s`, return *the **minimum** number of characters you need to delete to make* `s` ***good**.*

The **frequency** of a character in a string is the number of times it appears in the string. For example, in the string `"aab"`, the **frequency** of `'a'` is `2`, while the **frequency** of `'b'` is `1`.

**Example 1:**

```
**Input:** s = "aab"
**Output:** 0
**Explanation:** s is already good.
```

**Example 2:**

```
**Input:** s = "aaabbbcc"
**Output:** 2
**Explanation:** You can delete two 'b's resulting in the good string "aaabcc".
Another way it to delete one 'b' and one 'c' resulting in the good string "aaabbc".
```

**Example 3:**

```
**Input:** s = "ceabaacb"
**Output:** 2
**Explanation:** You can delete both 'c's resulting in the good string "eabaab".
Note that we only care about characters that are still in the string at the end (i.e. frequency of 0 is ignored).
```

**Constraints:**

* `1 <= s.length <= 105`
* `s` contains only lowercase English letters.

## ac

```java
```