Solve three interview coding problems

This interview report described three coding tasks: 1. **Generate a run-length spoken sequence** Start with `s1 = "1"`. To build the next term, read the current string from left to right, group consecutive identical digits, and write each group as `<count><digit>`. For example, `"1" -> "11" -> "21" -> "1211"`. Given an integer `n`, return the `n`th term of the sequence. 2. **Count substrings that can be rearranged into a palindrome** Given a list of lowercase strings, compute the answer for each string independently. For a single string `s`, count how many non-empty contiguous substrings can be rearranged, by swapping characters, into a palindrome. Example: for `s = "aabb"`, the answer is `9`. 3. **Replace wildcards to satisfy a digit-sum constraint** You are given a numeric string such as `"08??840"`, a target sum `24`, and the rule that each `?` must be replaced by a digit from `0` to `8` inclusive. Return all possible completed strings whose digits sum to the target. For example, valid outputs for `"08??840"` with target sum `24` are: - `"0804840"` - `"0813840"` - `"0822840"` - `"0840840"` Return the complete set of valid strings in any order.