What is the mistake in this Sudoku checker code?

In summary: 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)
  • #1
doktorwho
181
6

Homework Statement


Python:
# Sudoku [[PLAIN]http://en.wikipedia.org/wiki/Sudoku][/PLAIN] 
# 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 don't 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?
 
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  • #2
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.
 
  • #3
phyzguy said:
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 can't see what it is.
 
  • #4
Got it :D
 
  • #5
What about this one? (since you found your answer)
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
 

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