CodingInterviewQuestions/Leetcode/Leetcode Problem 36 Valid Sudoku.txt at master · akuchotrani/CodingInterviewQuestions · GitHub

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36. Valid Sudoku
Determine if a 9x9 Sudoku board is valid. Only the filled cells need to be validated according to the following rules:

Each row must contain the digits 1-9 without repetition.
Each column must contain the digits 1-9 without repetition.
Each of the 9 3x3 sub-boxes of the grid must contain the digits 1-9 without repetition.

A partially filled sudoku which is valid.

The Sudoku board could be partially filled, where empty cells are filled with the character '.'.

Example 1:

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
Example 2:

Input:
[
  ["8","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: false
Explanation: Same as Example 1, except with the 5 in the top left corner being
    modified to 8. Since there are two 8's in the top left 3x3 sub-box, it is invalid.
Note:

A Sudoku board (partially filled) could be valid but is not necessarily solvable.
Only the filled cells need to be validated according to the mentioned rules.
The given board contain only digits 1-9 and the character '.'.
The given board size is always 9x9.


def isValidBoard(self, row, col, board):
currentValueDecision = board[row][col]

#Check the row for validity. Go through cols and check for repeated value
for i in range(len(board[0])):
    if i != col and board[row][i] == currentValueDecision:
        print(F"Cannot place {currentValueDecision} at position {row},{col} Error from row validity")
        return False

#Check the col for validity. Go through the rows and check for repeated value
for i in range(len(board)):
    if i!= row and board[i][col] == currentValueDecision:
        print(F"Cannot place {currentValueDecision} at position {row},{col} Error from col validity")
        return False

#Check the sub grid
subGridRegionSize = 3

#We do this to trim out the decimal from the row and col index to calculate the top corners
verticalRowIndex = (int)(row/subGridRegionSize)
horizontalColIndex = (int)(col/subGridRegionSize)

#Calculate the top corners
topRowIndex = subGridRegionSize*verticalRowIndex
topColIndex = subGridRegionSize*horizontalColIndex

#Loop through the sub grid and check for repetitions
for i in range(subGridRegionSize):
    for j in range(subGridRegionSize):
        if board[topRowIndex + i][topColIndex + j] == currentValueDecision and ((topRowIndex+i) != row and (topColIndex+j) != col):
            print(F"Cannot place {currentValueDecision} at position {row},{col} Error from grid validity")
            return False

return True

def isValidSudoku(self, board: List[List[str]]) -> bool:
return self.isGivenSudokuValid(board)


#Backtracking sudoku solver. There's bug in the code it fails on few test cases need to debug

def solveSudoku(self, row, col, board) -> bool:

#         #Goal condition for solving individual row
#         if col == len(board[0]):
#             col = 0
#             row += 1
#             print(F"proceeding to the next row: {row}")

#         #End goal condition
#         if row == len(board):
#             print(F"Solved the board")
#             return True

#         #Default value already present so no need to solve for that cell
#         if board[row][col] != '.':
#             return self.solveSudoku(row, col+1, board)

#         #Go through the choice/decision space
#         for value in range(1,10):
#             board[row][col] = (str)(value)
#             print(F"Trying to place value: {value} at position {row},{col}")
#             if self.isValidBoard(row, col, board):
#                 print("This was valid")
#                 #Solve the next cell through a recursive call
#                 if(self.solveSudoku(row, col+1, board)):
#                     return True
#             #If the current decision did not work out then revert and try for next value
#             board[row][col] = "."

#         return False