Python/project_euler/problem_76/sol1.py

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"""
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Counting Summations
Problem 76
It is possible to write five as a sum in exactly six different ways:
4 + 1
3 + 2
3 + 1 + 1
2 + 2 + 1
2 + 1 + 1 + 1
1 + 1 + 1 + 1 + 1
How many different ways can one hundred be written as a sum of at least two
positive integers?
"""
from __future__ import print_function
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try:
xrange # Python 2
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except NameError:
xrange = range # Python 3
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def partition(m):
"""Returns the number of different ways one hundred can be written as a sum
of at least two positive integers.
>>> partition(100)
190569291
>>> partition(50)
204225
>>> partition(30)
5603
>>> partition(10)
41
>>> partition(5)
6
>>> partition(3)
2
>>> partition(2)
1
>>> partition(1)
0
"""
memo = [[0 for _ in xrange(m)] for _ in xrange(m + 1)]
for i in xrange(m + 1):
memo[i][0] = 1
for n in xrange(m + 1):
for k in xrange(1, m):
memo[n][k] += memo[n][k - 1]
if n > k:
memo[n][k] += memo[n - k - 1][k]
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return memo[m][m - 1] - 1
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if __name__ == "__main__":
print(partition(int(str(input()).strip())))