Group Strings By Anagram Signature

Question

The question asks the candidate to group strings that are anagrams of each other based on their anagram signature.

Codemia · Accepted Answer

To group strings by their anagram signatures, we can use a hash map (dictionary) where the key is the sorted version of the string (the anagram signature) and the value is a list of strings that match that signature. The steps are as follows:
1. Initialize an empty dictionary.
2. Iterate through each string, sort it, and use the sorted string as the key.
3. Append the original string to the list corresponding to that key in the dictionary.

Here is the Python implementation of the above approach:
```python
from collections import defaultdict

def group_anagrams(strs):
    anagrams = defaultdict(list)
    for s in strs:
        key = ''.join(sorted(s))
        anagrams[key].append(s)
    return list(anagrams.values())
```
This function takes a list of strings and returns a list of lists, where each inner list contains strings that are anagrams.

The time complexity of this solution is O(N * K log K), where N is the number of strings and K is the maximum length of a string. This is due to the sorting operation for each string. The space complexity is O(N) for storing the list of grouped anagrams in the dictionary.

Consider edge cases such as:
- An empty list of strings should return an empty list.
- Strings with different cases (e.g., 'abc' vs 'ABC') should be treated as different unless specified otherwise. We can handle this by normalizing the case before sorting.

Interviewers will look for clarity in your explanation and your ability to articulate your thought process. They will also assess your coding style, efficiency, and how well you handle edge cases and complexity analysis.

Group Strings By Anagram Signature

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