Determine if a Sudoku is valid, according to:
The Sudoku board could be partially filled, where empty cells are filled with the character '.'.
A partially filled sudoku which is valid.
Note:
A valid Sudoku board (partially filled) is not necessarily solvable. Only the filled cells need to be validated.
Solution
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public class { public boolean isValidSudoku(char[][] board) { for(int i=0; i < 9; i++) { HashSet<Character> row = new HashSet<Character>(); HashSet<Character> col = new HashSet<Character>(); HashSet<Character> cube = new HashSet<Character>(); for(int j=0; j < 9; j++) { if(board[i][j] != '.' && !row.add(board[i][j])) return false; if(board[j][i] != '.' && !col.add(board[j][i])) return false; int cuberow = 3*(i/3); int cubecol = 3*(i%3); if(board[cuberow+j/3][cubecol+j%3]!='.'&&!cube.add(board[cuberow+j/3][cubecol+j%3])) return false; } } return true; } }
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