LeetCode Q36: Valid Sudoku

Determine if a Sudoku is valid, according to: Sudoku Puzzles - The Rules.

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.

Use array to mark the access of elements in board. For each element in board, check three arrays in the same time.

	class Solution {
	public:
	bool isValidSudoku(vector<vector<char>>& board) {
	vector<vector<int> > flag(27, vector<int>(9, 0));
	for(int row=0; row<9; row++){
	for(int col=0; col<9; col++){
	char c = board[row][col];
	if(c=='.')
	continue;
	int n = c-'1';
	// row flag
	if(flag[0+row][n]==0)
	flag[0+row][n]=1;
	else
	return false;
	// col flag
	if(flag[9+col][n]==0)
	flag[9+col][n]=1;
	else
	return false;
	// chunk flag
	int idx=(ceil((row+1)/3.0)-1)*3+(ceil((col+1)/3.0)-1);
	if(flag[18+idx][n]==0)
	flag[18+idx][n]=1;
	else
	return false;
	}
	}
	return true;
	}
	};

view raw Q36ValidSudoku.cpp hosted with ❤ by GitHub