Add solution for string compression

Author: kwnna15

array/string-compression/README.md

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+# 443. String Compression
+
+## Description
+See https://leetcode.com/problems/string-compression/description/
+
+## Problem
+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.
+
+You must write an algorithm that uses only constant 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".
+```
+
+## Constraints
+
+```
+1 <= chars.length <= 2000
+chars[i] is a lowercase English letter, uppercase English letter, digit, or symbol.
+```

array/string-compression/stringcompression.py

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+def compress(chars: list[str]) -> int:
+    if len(chars) == 0:
+        return 0
+    read, write = 0, 0
+    while read < len(chars):
+        char = chars[read]
+        count = 0
+        while read < len(chars) and chars[read] == char:
+            read += 1
+            count += 1
+        chars[write] = char
+        write += 1
+
+        if count > 1:
+            for digit in str(count):
+                chars[write] = digit
+                write += 1
+    return write

array/string-compression/stringcompression_test.py

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+from stringcompression import compress
+
+def test_example_1():
+    chars = ["a","a","b","b","c","c","c"]
+    assert compress(chars) == 6
+    assert chars[:6] == ["a","2","b","2","c","3"]
+
+def test_example_2():
+    chars = ["a"]
+    assert compress(chars) == 1
+    assert chars[:1] == ["a"]
+
+def test_example_3():
+    chars = ["a","b","b","b","b","b","b","b","b","b","b","b","b"]
+    assert compress(chars) == 4
+    assert chars[:4] == ["a","b","1","2"]
+
+def test_example_4():
+    chars = ["a","a","a","b","b","a","a"]
+    assert compress(chars) == 6
+    assert chars[:6] == ["a","3","b","2","a","2"]
+
+def test_example_5():
+    chars = ["a","a","a","a","a","a","a","a","a","a"]
+    assert compress(chars) == 3
+    assert chars[:3] == ["a","1","0"]