The core trie implementation wasn't too bad, I got through insert and prefix count without much trouble.
Start by proposing a trie (prefix tree) as the core data structure, explaining how each node stores a count of strings passing through it to support prefix counting in O(L) time. Then address the follow-ups by normalizing inputs: for case-insensitivity, lowercase all characters before insertion and query; for stripping trailing digits, preprocess strings to remove trailing digits before any operation. Discuss trade-offs such as memory overhead and potential alternatives like hash maps with prefix keys.
Pro tip: Mention that the trie can be augmented with a count at each node to avoid traversing the entire subtree, and that normalization should be applied consistently to both insertions and queries to maintain correctness. Also, consider edge cases like empty strings and strings that become empty after stripping digits.
Ask about expected input size, character set, and whether updates (deletions) are needed. Confirm that prefix counting should be exact and efficient.
Describe a trie where each node has a count of how many strings pass through it. Insertion increments counts along the path; prefix query traverses to the prefix node and returns its count.
State that insertion and query take O(L) time where L is string length, and memory is O(total characters). Compare with alternatives like hash maps storing all prefixes, which use more space but may be faster for certain queries.
Normalize all input strings to lowercase (or uppercase) before insertion and query. This ensures that 'Apple' and 'apple' are treated the same.
Preprocess strings by removing trailing digits (e.g., using a regex or loop) before insertion and query. Ensure this is done consistently and consider edge cases like strings that become empty.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.
Start by clarifying edge cases like an empty list or removing the head, then propose a two-pointer (prev/curr) traversal with a dummy head to simplify head removal. Walk through the pointer updates, analyze O(n) time and O(1) space, and test with examples including consecutive removals.
Pro tip: Use a dummy node pointing to the head to avoid special-casing head removal, and explicitly mention that you're not freeing memory in languages like C/C++ unless asked—this shows awareness of memory management.
Ask about empty list, all nodes matching, no matches, and whether the list is singly linked. Confirm if memory deallocation is needed.
Propose using a dummy head node and two pointers (prev and curr) to handle removal uniformly, including the head.
Initialize dummy.next = head, prev = dummy, curr = head. While curr, if curr.val == target, set prev.next = curr.next; else prev = curr. Move curr = curr.next. Return dummy.next.
State O(n) time and O(1) space. Test with examples: empty list, head removal, consecutive removals, and no removal.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.