After delving into the Sudoku Solution Validator algorithm, I stumbled upon an interesting example. The code seems to work perfectly and validates the solution. However, one thing that perplexes me is why there is a N-2 in the for loops when trying to validate a block. If N = 9 and the board is 9 * 9, shouldn't it stay as 9 instead of being changed to 7?
I experimented by removing the -2 and sticking with just N, but I didn't notice any changes in my console output.
Here is the link for reference.
Thank you!!
<script>
// JavaScript program to implement
// the above approach
var N = 9;
// Function to check if all elements
// of the board[][] array store
// value in the range[1, 9]
function isinRange(board)
{
// Traverse board[][] array
for(var i = 0; i < N; i++)
{
for(var j = 0; j < N; j++)
{
// Check if board[i][j]
// lies in the range
if (board[i][j] <= 0 ||
board[i][j] > 9)
{
return false;
}
}
}
return true;
}
// Function to check if the solution
// of sudoku puzzle is valid or not
function isValidSudoku(board)
{
// Check if all elements of board[][]
// stores value in the range[1, 9]
if (isinRange(board) == false)
{
return false;
}
// Stores unique value
// from 1 to N
var unique = Array(N+1).fill(false);
// Traverse each row of
// the given array
for(var i = 0; i < N; i++)
{
unique = Array(N+1).fill(false);
// Traverse each column
// of current row
for(var j = 0; j < N; j++)
{
// Stores the value
// of board[i][j]
var Z = board[i][j];
// Check if current row
// stores duplicate value
if (unique[Z])
{
return false;
}
unique[Z] = true;
}
}
// Traverse each column of
// the given array
for(var i = 0; i < N; i++)
{
// Initialize unique[]
// array to false
unique = Array(N+1).fill(false);
// Traverse each row
// of current column
for(var j = 0; j < N; j++)
{
// Stores the value
// of board[j][i]
var Z = board[j][i];
// Check if current column
// stores duplicate value
if (unique[Z])
{
return false;
}
unique[Z] = true;
}
}
// Traverse each block of
// size 3 * 3 in board[][] array
for(var i = 0; i < N - 2; i += 3)
{
// j stores first column of
// each 3 * 3 block
for(var j = 0; j < N - 2; j += 3)
{
// Initialize unique[]
// array to false
unique = Array(N+1).fill(false);
// Traverse current block
for(var k = 0; k < 3; k++)
{
for(var l = 0; l < 3; l++)
{
// Stores row number
// of current block
var X = i + k;
// Stores column number
// of current block
var Y = j + l;
// Stores the value
// of board[X][Y]
var Z = board[X][Y];
// Check if current block
// stores duplicate value
if (unique[Z])
{
return false;
}
unique[Z] = true;
}
}
}
}
// If all conditions satisfied
return true;
}
// Driver Code
var board = [ [ 7, 9, 2, 1, 5, 4, 3, 8, 6 ],
[ 6, 4, 3, 8, 2, 7, 1, 5, 9 ],
[ 8, 5, 1, 3, 9, 6, 7, 2, 4 ],
[ 2, 6, 5, 9, 7, 3, 8, 4, 1 ],
[ 4, 8, 9, 5, 6, 1, 2, 7, 3 ],
[ 3, 1, 7, 4, 8, 2, 9, 6, 5 ],
[ 1, 3, 6, 7, 4, 8, 5, 9, 2 ],
[ 9, 7, 4, 2, 1, 5, 6, 3, 8 ],
[ 5, 2, 8, 6, 3, 9, 4, 1, 7 ] ];
if (isValidSudoku(board))
{
document.write("Valid");
}
else
{
document.write("Not Valid");
}
</script>