# ---
# title: 443. String Compression
# id: problem443
# author: Tian Jun
# date: 2020-10-31
# difficulty: Medium
# categories: String
# link: <https://leetcode.com/problems/string-compression/description/>
# hidden: true
# ---
# 
# Given an array of characters `chars`, compress it using the following
# algorithm:
# 
# Begin with an empty string `s`. For each group of **consecutive repeating
# characters** in `chars`:
# 
#   * If the group's length is 1, append the character to `s`.
#   * Otherwise, append the character followed by the group's length.
# 
# 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`.
# 
# After you are done **modifying the input array** , return _the new length of
# the array_.
# 
# 
# 
# **Follow up:**  
# Could you solve it using only `O(1)` extra space?
# 
# 
# 
# **Example 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:**
# 
#     
#     
#     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:**
# 
#     
#     
#     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".
# 
# **Example 4:**
# 
#     
#     
#     Input: chars = ["a","a","a","b","b","a","a"]
#     Output: Return 6, and the first 6 characters of the input array should be: ["a","3","b","2","a","2"].
#     Explanation:  The groups are "aaa", "bb", and "aa". This compresses to "a3b2a2". Note that each group is independent even if two groups have the same character.
#     
# 
# 
# 
# **Constraints:**
# 
#   * `1 <= chars.length <= 2000`
#   * `chars[i]` is a lower-case English letter, upper-case English letter, digit, or symbol.
# 
# 
## @lc code=start
using LeetCode

## add your code here:
## @lc code=end
