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# 0420. Strong Password Checker

<https://leetcode.com/problems/strong-password-checker>

## Description

A password is considered strong if the below conditions are all met:

* It has at least `6` characters and at most `20` characters.
* It contains at least **one lowercase** letter, at least **one uppercase** letter, and at least **one digit**.
* It does not contain three repeating characters in a row (i.e., `"...aaa..."` is weak, but `"...aa...a..."` is strong, assuming other conditions are met).

Given a string `password`, return *the minimum number of steps required to make `password` strong. if `password` is already strong, return `0`.*

In one step, you can:

* Insert one character to `password`,
* Delete one character from `password`, or
* Replace one character of `password` with another character.

**Example 1:**

```
**Input:** password = "a"
**Output:** 5
```

**Example 2:**

```
**Input:** password = "aA1"
**Output:** 3
```

**Example 3:**

```
**Input:** password = "1337C0d3"
**Output:** 0
```

**Constraints:**

* `1 <= password.length <= 50`
* `password` consists of letters, digits, dot `'.'` or exclamation mark `'!'`.

## ac

```java
```