Skip to content

Added Optimal Merge Pattern Algorithm #5274

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
merged 2 commits into from
Oct 14, 2021
Merged
Changes from all commits
Commits
File filter

Filter by extension

Filter by extension

Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
56 changes: 56 additions & 0 deletions greedy_methods/optimal_merge_pattern.py
Original file line number Diff line number Diff line change
@@ -0,0 +1,56 @@
"""
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
# Consider two files with minimum cost to be merged
for i 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()