Clarify the encoding format and edge cases, then design a single-pass parser that accumulates digits until a letter is encountered, at which point it emits the repeated pattern. Discuss time/space complexity and potential optimizations like streaming or handling large counts.
Pro tip: Mention that you would validate the input and handle malformed tokens gracefully, and consider whether the output should be built as a list of strings for efficiency before joining.
Ask questions to confirm the exact encoding rules, such as whether counts can be multi-digit, if patterns can be empty, and what characters are allowed. Also clarify expected input size and output format.
Describe a linear scan: iterate through the string, building the current count when digits are seen, and when a letter is encountered, append the letter repeated count times to the result. Reset the count after each token.
Discuss handling of invalid inputs (e.g., missing count, zero count, non-digit/non-letter characters) and how to report errors. Consider empty input and very large counts that could cause memory issues.
State that time complexity is O(n + m) where n is input length and m is output length, and space is O(m) for the output. Mention alternatives like streaming output or using a generator to avoid building the entire string in memory.
Walk through a few test cases, including simple ones like '3a2b' -> 'aaabb', multi-digit counts like '12a', and edge cases like '0a' or 'a' (if invalid).
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.
Clarify the RLE format and constraints, then propose a dynamic programming solution that considers all possible pattern lengths up to K. Discuss trade-offs between time and space complexity, and test with edge cases.
Pro tip: Mention that the optimal encoding might not be greedy; DP is needed to handle cases where shorter patterns lead to better overall compression. Also, discuss how to handle patterns that repeat non-consecutively.
Ask clarifying questions about the RLE format (e.g., how counts are encoded, whether patterns can overlap) and constraints (string length, K value). Confirm that the goal is to minimize total characters in the encoded output.
Define dp[i] as the minimum encoded length for the prefix ending at index i. Consider transitions by trying all pattern lengths L from 1 to K that can be repeated consecutively starting at some position.
For each position, precompute the maximum number of times each pattern of length L repeats consecutively. Use this to efficiently compute dp transitions, possibly with a sliding window or precomputed arrays.
Account for the character cost of encoding the count (e.g., number of digits) and the pattern itself. Ensure the encoding format is correctly applied, including any delimiters.
Analyze time and space complexity (e.g., O(N*K) time). Walk through examples, including edge cases like K=1, all same characters, and patterns that repeat non-consecutively.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.