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fixed error in factorial.py #1888

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Merged
merged 5 commits into from
Aug 5, 2020
Merged

fixed error in factorial.py #1888

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49654da
Update factorial.py
SandersLin Apr 17, 2020
545fc89
Merge branch 'master' into patch-33
l3str4nge Jun 23, 2020
e95fb72
updating DIRECTORY.md
Jun 23, 2020
b7ecbf6
Update dynamic_programming/factorial.py
cclauss Aug 5, 2020
6a038a1
Update factorial.py
cclauss Aug 5, 2020
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4 changes: 4 additions & 0 deletions DIRECTORY.md
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Original file line number Diff line number Diff line change
Expand Up @@ -16,6 +16,7 @@
* [All Subsequences](https://github.com/TheAlgorithms/Python/blob/master/backtracking/all_subsequences.py)
* [Coloring](https://github.com/TheAlgorithms/Python/blob/master/backtracking/coloring.py)
* [Hamiltonian Cycle](https://github.com/TheAlgorithms/Python/blob/master/backtracking/hamiltonian_cycle.py)
* [Knight Tour](https://github.com/TheAlgorithms/Python/blob/master/backtracking/knight_tour.py)
* [Minimax](https://github.com/TheAlgorithms/Python/blob/master/backtracking/minimax.py)
* [N Queens](https://github.com/TheAlgorithms/Python/blob/master/backtracking/n_queens.py)
* [Rat In Maze](https://github.com/TheAlgorithms/Python/blob/master/backtracking/rat_in_maze.py)
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## Compression
* [Burrows Wheeler](https://github.com/TheAlgorithms/Python/blob/master/compression/burrows_wheeler.py)
* [Huffman](https://github.com/TheAlgorithms/Python/blob/master/compression/huffman.py)
* [Lempel Ziv](https://github.com/TheAlgorithms/Python/blob/master/compression/lempel_ziv.py)
* [Lempel Ziv Decompress](https://github.com/TheAlgorithms/Python/blob/master/compression/lempel_ziv_decompress.py)
* [Peak Signal To Noise Ratio](https://github.com/TheAlgorithms/Python/blob/master/compression/peak_signal_to_noise_ratio.py)

## Computer Vision
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* [Longest Increasing Subsequence O(Nlogn)](https://github.com/TheAlgorithms/Python/blob/master/dynamic_programming/longest_increasing_subsequence_o(nlogn).py)
* [Longest Sub Array](https://github.com/TheAlgorithms/Python/blob/master/dynamic_programming/longest_sub_array.py)
* [Matrix Chain Order](https://github.com/TheAlgorithms/Python/blob/master/dynamic_programming/matrix_chain_order.py)
* [Max Non Adjacent Sum](https://github.com/TheAlgorithms/Python/blob/master/dynamic_programming/max_non_adjacent_sum.py)
* [Max Sub Array](https://github.com/TheAlgorithms/Python/blob/master/dynamic_programming/max_sub_array.py)
* [Max Sum Contiguous Subsequence](https://github.com/TheAlgorithms/Python/blob/master/dynamic_programming/max_sum_contiguous_subsequence.py)
* [Minimum Partition](https://github.com/TheAlgorithms/Python/blob/master/dynamic_programming/minimum_partition.py)
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33 changes: 11 additions & 22 deletions dynamic_programming/factorial.py
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@@ -1,36 +1,25 @@
# Factorial of a number using memoization
result = [-1] * 10
result[0] = result[1] = 1

from functools import lru_cache

def factorial(num):

@lru_cache
def factorial(num: int) -> int:
"""
>>> factorial(7)
5040
>>> factorial(-1)
'Number should not be negative.'
>>> [factorial(i) for i in range(5)]
[1, 1, 2, 6, 24]
Traceback (most recent call last):
...
ValueError: Number should not be negative.
>>> [factorial(i) for i in range(10)]
[1, 1, 2, 6, 24, 120, 720, 5040, 40320, 362880]
"""

if num < 0:
return "Number should not be negative."
if result[num] != -1:
return result[num]
else:
result[num] = num * factorial(num - 1)
# uncomment the following to see how recalculations are avoided
# print(result)
return result[num]
raise ValueError("Number should not be negative.")

return 1 if num in (0, 1) else num * factorial(num - 1)

# factorial of num
# uncomment the following to see how recalculations are avoided
# result=[-1]*10
# result[0]=result[1]=1
# print(factorial(5))
# print(factorial(3))
# print(factorial(7))

if __name__ == "__main__":
import doctest
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