leetcode_gym/_problems/validateSudoku.md

layout, title, last_solved, category, leetcode_url, status

layout	title	last_solved	category	leetcode_url	status
page	Validate Sudoku	2020-06-10	matrix	https://leetcode.com/problems/valid-sudoku/	Solved

Problem

Input:
[
  ["5","3",".",".","7",".",".",".","."],
  ["6",".",".","1","9","5",".",".","."],
  [".","9","8",".",".",".",".","6","."],
  ["8",".",".",".","6",".",".",".","3"],
  ["4",".",".","8",".","3",".",".","1"],
  ["7",".",".",".","2",".",".",".","6"],
  [".","6",".",".",".",".","2","8","."],
  [".",".",".","4","1","9",".",".","5"],
  [".",".",".",".","8",".",".","7","9"]
]
Output: true

Solution

{% highlight python %}

def validateBoard(bo):

rows = [ set() for i in range(9) ]
cols = [ set() for i in range(9) ]
boxes = [ set() for i in range(9) ]

for i in range(9):
    for j in range(9):

        val = bo[i][j]
        if val==".":
            continue


        # validate row
        if val in rows[i]:

            print( val + "already in row %s" % i )
            return False
        else:
            rows[i].add( val )

        # validate col
        if val in cols[j]:

            print( val + "already in col %s" % j )
            return False
        else:
            cols[j].add( val )

        # validate box
        k = (i//3)*3 + (j//3)
        if val in boxes[k]:

            print( val + "already in box %s" % k )
            return False
        else:
            boxes[k].add( val )

return True

{% endhighlight %}