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Topic: Frequency of substring (Read 2312 times) |
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hemanshu
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Frequency of substring
« on: Mar 1st, 2011, 1:50am » |
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I want to rank the substrings occurring multiple times in a string according to their frequency of occurrence in a string. example :
strings is abcdabceabcfabcabcd
ans is abc : 5
abcd:2
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towr
wu::riddles Moderator
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Re: Frequency of substring
« Reply #1 on: Mar 1st, 2011, 8:43am » |
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Sounds like something you could use a trie for.
A trie can give you all the positions where a substring occurs, so just counting that number of positions will give you the frequencies.
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Grimbal
wu::riddles Moderator
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Re: Frequency of substring
« Reply #2 on: Mar 1st, 2011, 9:50am » |
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I would have proposed a suffix tree.
It is not very different from tries (prefix trees). But it adds pointers that make it possible to build the tree from a string in O(n) time and memory,
So if your string could be a rather thick book, this would be worth considering.
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solid
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Re: Frequency of substring
« Reply #3 on: Sep 4th, 2011, 3:53pm » |
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Can be solved by 2 ways:
1) Suffix Tree
2) Robin Karp Algorithm: Calculate Hash for pattern and text and then find the same hash in text.
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