Re: [Tutor] Tutor Digest, Vol 102, Issue 48

[Alan Gauld]

On 21/08/12 06:12, Osemeka Osuagwu wrote:


right_product(row, col) for (row = 0, col = 18) I had anticipated this
and added the "if col>len(data[row])-3:" statement


But because of zero indexing you need this to be either:

if col >= len(data[row])-3:

or

if col > len(data[row])-4:

ie. if row length is 10 the indexes go from 0-9 so the
highest index you can use is 6.

However you have similar problems in other places, such
as your main function. Consider:

for row in range(len(data)):
for col in range(len(data[row])):
if right_product(row, col) > prod:
source = [data[row][i] for i in range(col, col+4)]

what happens when col gets bigger than len(row)-4?

if down_right_product(row, col) > prod:
source = [data[row+each][col+each] for each in range(4)]

And this is even worse because both additions could blow up.

It's probably better  if you can fix it in the for loops
rather than putting if guards in.


HTH
--
Alan G
Author of the Learn to Program web site
http://www.alan-g.me.uk/

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Re: [Tutor] Tutor Digest, Vol 102, Issue 48

[Osemeka Osuagwu]

Dear Mark,

> I can't see a Python array anywhere.  Do you mean the list of lists? :)
>
>> THE CODE
>
> [snipped as it's been mangled, was it posted in html and not plain text
> or what?  I'm too lazy to unmangle it, others might be kinder]
>
Again, my bad. Here's the code in plain text:

''#---
# Name:Project Euler Problem 11
# Purpose:Project Euler 11
#
# Author: Abasiemeka
#
# Created:23-07-2012
# Copyright: (c) Abasiemeka 2012
# Licence: 
#---

data = [[ 8, 02, 22, 97, 38, 15, 00, 40, 00, 75, 04, 05, 07, 78, 52,
12, 50, 77, 91,  8],
[49, 49, 99, 40, 17, 81, 18, 57, 60, 87, 17, 40, 98, 43, 69,
48, 04, 56, 62, 00],
[81, 49, 31, 73, 55, 79, 14, 29, 93, 71, 40, 67, 53, 88, 30,
03, 49, 13, 36, 65],
[52, 70, 95, 23, 04, 60, 11, 42, 69, 24, 68, 56, 01, 32, 56,
71, 37, 02, 36, 91],
[22, 31, 16, 71, 51, 67, 63, 89, 41, 92, 36, 54, 22, 40, 40,
28, 66, 33, 13, 80],
[24, 47, 32, 60, 99, 03, 45, 02, 44, 75, 33, 53, 78, 36, 84,
20, 35, 17, 12, 50],
[32, 98, 81, 28, 64, 23, 67, 10, 26, 38, 40, 67, 59, 54, 70,
66, 18, 38, 64, 70],
[67, 26, 20, 68, 02, 62, 12, 20, 95, 63, 94, 39, 63,  8, 40,
91, 66, 49, 94, 21],
[24, 55, 58, 05, 66, 73, 99, 26, 97, 17, 78, 78, 96, 83, 14,
88, 34, 89, 63, 72],
[21, 36, 23,  9, 75, 00, 76, 44, 20, 45, 35, 14, 00, 61, 33,
97, 34, 31, 33, 95],
[78, 17, 53, 28, 22, 75, 31, 67, 15, 94, 03, 80, 04, 62, 16,
14,  9, 53, 56, 92],
[16, 39, 05, 42, 96, 35, 31, 47, 55, 58, 88, 24, 00, 17, 54,
24, 36, 29, 85, 57],
[86, 56, 00, 48, 35, 71, 89, 07, 05, 44, 44, 37, 44, 60, 21,
58, 51, 54, 17, 58],
[19, 80, 81, 68, 05, 94, 47, 69, 28, 73, 92, 13, 86, 52, 17,
77, 04, 89, 55, 40],
[04, 52,  8, 83, 97, 35, 99, 16, 07, 97, 57, 32, 16, 26, 26,
79, 33, 27, 98, 66],
[88, 36, 68, 87, 57, 62, 20, 72, 03, 46, 33, 67, 46, 55, 12,
32, 63, 93, 53, 69],
[04, 42, 16, 73, 38, 25, 39, 11, 24, 94, 72, 18,  8, 46, 29,
32, 40, 62, 76, 36],
[20, 69, 36, 41, 72, 30, 23, 88, 34, 62, 99, 69, 82, 67, 59,
85, 74, 04, 36, 16],
[20, 73, 35, 29, 78, 31, 90, 01, 74, 31, 49, 71, 48, 86, 81,
16, 23, 57, 05, 54],
[01, 70, 54, 71, 83, 51, 54, 69, 16, 92, 33, 48, 61, 43, 52,
01, 89, 19, 67, 48]]

def down_right_product(row, col):
if (row>len(data)-3) or (col>len(data[row])-3):
return 1
else:
return reduce(lambda x,y:x*y, [data[row+each][col+each] for
each in range(4)])

def down_left_product(row, col):
if (row>len(data)-3) or (col<3):
return 1
else:
return reduce(lambda x,y:x*y, [data[row-each][col-each] for
each in range(4)])

def right_product(row, col):
if col>len(data[row])-3:
return 0
else:
return reduce(lambda x,y:x*y, [data[row][i] for i in range(col, col+4)])

def down_product(row, col):
if row>len(data)-3:
return 1
else:
return reduce(lambda x,y:x*y, [data[i][col] for i in range(row, row+4)])


def main():
prod = 1
source = []
for row in range(len(data)):
for col in range(len(data[row])):
#print col, row
if right_product(row, col) > prod:
prod = right_product(row, col)
source = [data[row][i] for i in range(col, col+4)]

if down_product(row, col) > prod:
prod = down_product(row, col)
source = [data[i][col] for i in range(row, row+4)]

if down_right_product(row, col) > prod:
prod = down_right_product(row, col)
source = [data[row+each][col+each] for each in range(4)]

if down_left_product(row, col) > prod:
prod = down_left_product(row, col)
source = [data[row-each][col-each] for each in range(4)]
print 'Maximum product is %d from %l' %(prod, source)



if __name__ == '__main__':
main()


 THE ERROR
>>
>>
>> Traceback (most recent call last):
>>
>>File "C:\Windows.old\Users\Abasiemeka\Abasiemeka\GOOGLE
>> University\Python\Python Code\MyCode\Project Euler code\Project Euler
>> answer 11.py", line 84, in 
>>
>>  main()
>>
>>File "C:\Windows.old\Users\Abasiemeka\Abasiemeka\GOOGLE
>> University\Python\Python Code\MyCode\Project Euler code\Project Euler
>> answer 11.py", line 64, in main
>>
>>  if right_product(row, col) > prod:
>>
>>File "C:\Windows.old\Users\Abasiemeka\Abasiemeka\GOOGLE
>> University\Python\Python Code\MyCode\Project Euler code\Project Euler
>> answer 11.py", line 49, in right_product
>>
>>  return reduce(lambda x,y:x*y, [data[row][i] for i in range(col, col+4)])
>>
>> IndexError: list index out of range
>>
>>
>
> The usual way to chase a problem like this is to place print statements
> in approp