# A problem with python code

• Comp Sci

## Homework Statement

Python:
# Sudoku [[PLAIN]http://en.wikipedia.org/wiki/Sudoku][/PLAIN] [Broken]
# is a logic puzzle where a game
# is defined by a partially filled
# 9 x 9 square of digits where each square
# contains one of the digits 1,2,3,4,5,6,7,8,9.
# For this question we will generalize
# and simplify the game.

# Define a procedure, check_sudoku,
# that takes as input a square list
# of lists representing an n x n
# sudoku puzzle solution and returns the boolean
# True if the input is a valid
# sudoku square and returns the boolean False
# otherwise.

# A valid sudoku square satisfies these
# two properties:

#   1. Each column of the square contains
#       each of the whole numbers from 1 to n exactly once.

#   2. Each row of the square contains each
#       of the whole numbers from 1 to n exactly once.

# You may assume the the input is square and contains at
# least one row and column.

correct = [[1,2,3],
[2,3,1],
[3,1,2]]

incorrect = [[1,2,3,4],
[2,3,1,3],
[3,1,2,3],
[4,4,4,4]]

incorrect2 = [[1,2,3,4],
[2,3,1,4],
[4,1,2,3],
[3,4,1,2]]

incorrect3 = [[1,2,3,4,5],
[2,3,1,5,6],
[4,5,2,1,3],
[3,4,5,2,1],
[5,6,4,3,2]]

incorrect4 = [['a','b','c'],
['b','c','a'],
['c','a','b']]

incorrect5 = [ [1, 1.5],
[1.5, 1]]

def check_sudoku(p):
rows=[]
coloums=[]
t=0
for i in p:
for e in i:
if e not in rows:
rows.append(e)
else:
return False
rows=[]
while t<=len(p):
for i in p:
if i.pop() not in coloums:
coloums.append(i.pop())
else:
return False
coloums=[]
t += 1
return True

print check_sudoku(incorrect)
#>>> False

print check_sudoku(correct)
#>>> True

print check_sudoku(incorrect2)
#>>> False

print check_sudoku(incorrect3)
#>>> False

print check_sudoku(incorrect4)
#>>> False

print check_sudoku(incorrect5)
#>>> False

## Homework Equations

3. The Attempt at a Solution [/B]
I dont actually want you to correct me, i just want for you to point out where i made the mistake as my code output gives all as False. I was sure it correctly checked everything, i have no idea why its behaving this way. The first part must be correct but the second might be the problem. Do you see the mistake?

Last edited by a moderator:
• berkeman

phyzguy
I don't think your nested loop is doing what you think. Try putting a print statement after the "for e in i:" line that prints out e and rows. I think you will quickly see the problem.

I don't think your nested loop is doing what you think. Try putting a print statement after the "for e in i:" line that prints out e and rows. I think you will quickly see the problem.
I exchanged what should be rows and what coloums, for me the rows are the elements in a sublists and the coloums are respective elements in each list. When i delete the second part of the code and check just the rows everything is ok. I even messed up something to know ots false and it gives it as false. The problem is in the second part. After the while statement. I cant see what it is.

Got it :D

ChrisVer
Gold Member
Python:
def checker( board ):
for row in board:
memory_list=[]
for entry in row:
if not isinstance(entry, int) or (entry>len(board)) : return False # make sure that all sudoku inputs are integers, else break out with False
if (entry in memory_list) and (len(memory_list)!=0): return False #repeated integer in row
memory_list.append(entry)
for iCol in range(len(board)):
memory_list=[]
Column= [row[iCol] for row in board]
for entry in Column:
if (entry in memory_list) and (len(memory_list)!=0): return False
memory_list.append(entry)
return True