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943e03fc54
* Minor changes due to precommit * Update optimal_merge_pattern.py Co-authored-by: Christian Clauss <cclauss@me.com>
57 lines
1.6 KiB
Python
57 lines
1.6 KiB
Python
"""
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This is a pure Python implementation of the greedy-merge-sort algorithm
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reference: https://www.geeksforgeeks.org/optimal-file-merge-patterns/
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For doctests run following command:
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python3 -m doctest -v greedy_merge_sort.py
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Objective
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Merge a set of sorted files of different length into a single sorted file.
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We need to find an optimal solution, where the resultant file
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will be generated in minimum time.
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Approach
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If the number of sorted files are given, there are many ways
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to merge them into a single sorted file.
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This merge can be performed pair wise.
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To merge a m-record file and a n-record file requires possibly m+n record moves
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the optimal choice being,
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merge the two smallest files together at each step (greedy approach).
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"""
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def optimal_merge_pattern(files: list) -> float:
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"""Function to merge all the files with optimum cost
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Args:
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files [list]: A list of sizes of different files to be merged
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Returns:
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optimal_merge_cost [int]: Optimal cost to merge all those files
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Examples:
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>>> optimal_merge_pattern([2, 3, 4])
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14
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>>> optimal_merge_pattern([5, 10, 20, 30, 30])
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205
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>>> optimal_merge_pattern([8, 8, 8, 8, 8])
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96
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"""
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optimal_merge_cost = 0
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while len(files) > 1:
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temp = 0
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# Consider two files with minimum cost to be merged
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for i in range(2):
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min_index = files.index(min(files))
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temp += files[min_index]
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files.pop(min_index)
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files.append(temp)
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optimal_merge_cost += temp
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return optimal_merge_cost
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if __name__ == "__main__":
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import doctest
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doctest.testmod()
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