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Excellent processing time Still have to perform some good work on prime numbers! Signed-off-by: Julien Lengrand-Lambert <julien@lengrand.fr>
47 lines
1.3 KiB
Python
47 lines
1.3 KiB
Python
#!/usr/bin/env python
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'''
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Created on 8 feb. 2012
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@author: Julien Lengrand-Lambert
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DESCRIPTION: Solves problem 28 of Project Euler
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Starting with the number 1 and moving to the right in a clockwise direction a 5 by 5 spiral is formed as follows:
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21 22 23 24 25
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20 7 8 9 10
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19 6 1 2 11
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18 5 4 3 12
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17 16 15 14 13
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It can be verified that the sum of the numbers on the diagonals is 101.
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What is the sum of the numbers on the diagonals in a 1001 by 1001 spiral formed in the same way?
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'''
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def sum_diag(max_lines):
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"""
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Returns the sum of both diagonals of the square of max_lines size
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"""
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dsum = 1 # sum of diagonals
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cpt = 1 # number of lines processed
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val = 1 # value of the current place in the square
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inc = 0 # the increment between number for one line
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while cpt < max_lines:
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cpt += 2
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inc += 2
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for corner in range(4):
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val += inc
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dsum += val
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return dsum
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if __name__ == '__main__':
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# The major problem in there is to find the logic
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#n = 1 gives 1
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#n = 3 gives 3, 5, 7, 9 => +2
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#n = 5 gives 13, 17, 21, 25 => +4
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#n = 7 gives 31, 37, 43, 49 => +6
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#n = 9 gives 57, . . .
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print "Answer : %d " % (sum_diag(1001))
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