sequence

Difference between list, sequence and slice in Python?

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You’re mixing very different things in your question, so I’ll just answer a different question You are now asking about one of the most important interface in Python: iterable – it’s basically anything you can use like for elem in iterable. iterable has three descendants: sequence, generator and mapping. A sequence is a iterable with … Read more

How can I determine all possible ways a subsequence can be removed from a sequence?

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This problem can be solved in O(n*m + r) time, where r is the total length of the results, using the classic longest common subsequence algorithm. Once the table is made, as in Wikipedia’s example, replace it with a list of the cells with a diagonal arrow that also have a value corresponding with their … Read more

How do I create a sequence in MySQL?

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This is a solution suggested by the MySQl manual: If expr is given as an argument to LAST_INSERT_ID(), the value of the argument is returned by the function and is remembered as the next value to be returned by LAST_INSERT_ID(). This can be used to simulate sequences: Create a table to hold the sequence counter … Read more

Oracle SQL: Use sequence in insert with Select Statement

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Assuming that you want to group the data before you generate the key with the sequence, it sounds like you want something like INSERT INTO HISTORICAL_CAR_STATS ( HISTORICAL_CAR_STATS_ID, YEAR, MONTH, MAKE, MODEL, REGION, AVG_MSRP, CNT) SELECT MY_SEQ.nextval, year, month, make, model, region, avg_msrp, cnt FROM (SELECT ‘2010’ year, ’12’ month, ‘ALL’ make, ‘ALL’ model, REGION, … Read more

How to choose between UUIDs, autoincrement/sequence keys and sequence tables for database primary keys?

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UUIDs Unless these are generated “in increasing monotonic sequence” they can drastically hurt/fragment indexes. Support for UUID generation varies by system. While usable, I would not use a UUID as my primary clustered index/PK in most cases. If needed I would likely make it a secondary column, perhaps indexed, perhaps not. Some people argue that … Read more

Permutation algorithm without recursion? Java

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You should use the fact that when you want all permutations of N numbers there are N! possibilities. Therefore each number x from 1..N! encodes such a permutation. Here is a sample that iteratively prints out all permutations of a sting. private static void printPermutationsIterative(String string){ int [] factorials = new int[string.length()+1]; factorials[0] = 1; … Read more