L_H's blog

Problem C Div 2
By L_H, 10 years ago, In English

I am trying to solve http://codeforces.net/contest/514/problem/C but repeatedly getting wa at test 6.Tried a lot but can't figure out the problem...Link to my solution http://codeforces.net/contest/514/submission/9883601

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10 years ago, # |
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=(((str[j]-'a'+1)*(ll)pow(5,j))%mod); pow function is declared like double pow(double x, double n)
some powers of 5 will not fit into double and number will be truncated(size of double is 8 bytes).
Use your own Pow function to power number modulo mod.

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10 years ago, # |
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Your bug is in hash calculation: pow function is calculating result in double type. It won't work as you expect: pow can return something like 3e100, it won't be taken by modulo and will moreover loose a lot of significant digits.

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10 years ago, # |
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I think the solution with trie is better than the hashing one. I haven't perfectly analized your code but maybe the bug is that your hashing is not perfect so I suggest you to implement the trie solution, which is much easier

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10 years ago, # |
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Why you don't try with different bases?For example try with 37 or 71...

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