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