DSA Walkthrough - 07

Intro

• We have to find if the given sudoku is valid, we dont have to fill the values
• From the given constraints we have to check if it is satisfied, if so then we return the bool value

First approach

• At first, i thought of using 2 for loops and iterating 2 the matrix.
• For every row and column, we check if the given condition is satisfied, if not we return false.
• Here, i forgot one thing that we need to set to store the values initially and check if it already exists in the set.

Solution

• The solution is pretty straightforward.
• First we store the values in a set by iterating in rows and columns
• then we check the conditions by checking if the (r,val) && (val,c) is in the sett.
• If all the conditions are satisfied, then we add those into the set.
• At last we return True.

Code

class Solution:
    def isValidSudoku(self, board: List[List[str]]) -> bool:
        sett = set()
        for r in range(9):
	        for c in range(9):
		        val = board[r][c]
		        
		        if val == '.':
			        continue
			    if (r,val) in sett:
				    return False
				if (val,c) in sett:
					return False
				if (r//3,c//3,val) in sett:
					return False
				
				sett.add((r,val))
				sett.add((val,c))
				sett.add(r//3,r//3,val)
				
		return True

Conclusion

This got me thinking for a bit, but i feel like i should have solved this all by myself. But I did learn the pattern on how to store it in a set and use if for solving constraint based problems.