Write rle_encode(s) that compresses a string by replacing every run of equal consecutive characters with the run length followed by the character. A count of 1 is omitted.
Examples
Input: s = "aaabcc"
Output: "3ab2c"
Input: s = "abc"
Output: "abc"
Input: s = ""
Output: ""
Constraints
0 <= len(s) <= 10**5, letters only (no digits, so the output is unambiguous)- Runs can be longer than 9, so counts may have several digits
- Target: O(n) time
Goals
- Detect where a run of equal characters ends
- Build the output with a list and join
- Emit a count only when it carries information