Hash Practice CS FUN #61
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Grabbing this to grade! |
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Pretty good...
Since your anagrams solution uses a list rather than a dictionary, it has a much worse running time, and fails to demonstrate knowledge of the material. However as you seem to otherwise demonstrate that knowledge on the other problems, I am marking this Yellow. I encourage you to look at using a dictionary for your anagrams solution, and if successful, I'll move to Green.
I also added a quick naming note as well as some missing complexity calculations, but neither of those issues are major.
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| def grouped_anagrams(strings): | |||
| """ This method will return an array of arrays. | |||
| Each subarray will have strings which are anagrams of each other | |||
| Time Complexity: ? | |||
| Space Complexity: ? | |||
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Missing complexity calculations here but I haven't been dinging people for it, simply calling attention to it.
| for i in range(1, len(strings)): | ||
| cur_str = strings[i] | ||
| cur_str_dict = create_dict(cur_str) | ||
| if cur_str_dict in dict_list: |
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Calling in on a list takes O(n) time, so by using the list dict_list instead of a dictionary, your entire solution takes O(n^2) time. You can achieve O(n) time by replacing dict_list with a dictionary, and that is the intended solution given the material, so I'm going to mark this as Yellow and encourage you to attempt that solution.
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| def create_dict(word): |
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create_dict is a bit too generic of a name, I think I would call this something like create_frequency_dict, because otherwise, my expectation is that this just creates an arbitrary dictionary rather than the specific frequency dictionary that is created here.
Hash Table Practice
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Comprehension Questions
Quicker than searching for lists/arrays.
How can you judge if a hash function is good or not? |
Is there a perfect hash function? If so what is it? |
Describe a strategy to handle collisions in a hash table | 1. Resizing by copying all entries. 2. Incremental resizing.3.Monotonic keys.
Describe a situation where a hash table wouldn't be as useful as a binary search tree | Hash is for unordered collection vs. binary search tree is for storing an ordered collection
What is one thing that is more clear to you on hash tables now | This was very helpful to understand the bigger picture: https://www.freecodecamp.org/news/the-codeless-guide-to-hash/