String Compression

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Given an array of characters chars, compress it using the following algorithm:
给定一个字符 chars 数组，使用以下算法对其进行压缩：

Begin with an empty string s. For each group of consecutive repeating characters in chars:
以空字符串 s 开头。对于 中的 chars 每组连续重复字符：

• If the group's length is 1, append the character to s.
  如果组的长度为 1 ，则将字符追加到 s 。
• Otherwise, append the character followed by the group's length.
  否则，附加字符后跟组的长度。

The compressed string s should not be returned separately, but instead, be stored in the input character array chars. Note that group lengths that are 10 or longer will be split into multiple characters in chars.
压缩字符串 s 不应单独返回，而应存储在输入字符数组 chars 中。请注意，组长度为 或更长的组长度将在 中 chars 拆分为 10 多个字符。

After you are done modifying the input array, return the new length of the array.
修改完输入数组后，返回数组的新长度。

You must write an algorithm that uses only constant extra space.
您必须编写仅使用常量额外空间的算法。

Example 1: 示例 1：

Input: chars = ["a","a","b","b","c","c","c"] Output: Return 6, and the first 6 characters of the input array should be: ["a","2","b","2","c","3"] Explanation: The groups are "aa", "bb", and "ccc". This compresses to "a2b2c3".

Example 2: 示例 2：

Input: chars = ["a"] Output: Return 1, and the first character of the input array should be: ["a"] Explanation: The only group is "a", which remains uncompressed since it's a single character.

Example 3: 例3：

Input: chars = ["a","b","b","b","b","b","b","b","b","b","b","b","b"] Output: Return 4, and the first 4 characters of the input array should be: ["a","b","1","2"]. Explanation: The groups are "a" and "bbbbbbbbbbbb". This compresses to "ab12".

Constraints: 约束：

• 1 <= chars.length <= 2000
• chars[i] is a lowercase English letter, uppercase English letter, digit, or symbol.
  chars[i] 是小写英文字母、大写英文字母、数字或符号。