Compress Consecutive Chars

Run-length encode a string by collapsing consecutive identical characters.

string run-length compression

Write a function `compress(s: str) -> str` that performs run-length encoding on the input string `s`. For each maximal consecutive group of identical characters, output the character followed by the group length. If a character appears only once, still output the character followed by `1`. The input string contains only lowercase English letters. Return the compressed string.

Examples:
- `compress("aaabbc")` returns `"a3b2c1"`.
- `compress("a")` returns `"a1"`.
- `compress("")` returns `""`.

Constraints

- 0 <= len(s) <= 1000
- s consists of lowercase English letters only.

Example

>>> compress("aaabbc")
'a3b2c1'
>>> compress("a")
'a1'
>>> compress("")
''

8 points ~12 min

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Hints

Iterate through the string while keeping a count of the current character.

When the character changes, append the previous character and its count, then reset the count.

Remember to flush the last group after the loop.

Test Results

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