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.

题目中说的,只要当前已经填充的数字是合法的就可以,不一定要这个数独是有解.（下面说的九宫格都是指3*3的网格）

因此只需要判断9*9网格的每一行、每一列、9个小九宫格是否合法。即如果在每一行、每一列、每个9个小九宫格内，某个数字重复出现了，当前数独就是不合法的。

bool isValidSudoku(vector<vector<char> > &board) {
        // Note: The Solution object is instantiated only once.
		int row[9],col[9];
		
		for(int i = 0; i < 9; i++)
		{
			memset(row,0,sizeof(int)*9);
			memset(col,0,sizeof(int)*9);
			for(int j = 0; j < 9; j++)
			{
				if(board[i][j] != '.')
				{
					if(row[board[i][j]-'1'] > 0)return false;
					else row[board[i][j]-'1']++;
				}
				if(board[j][i] != '.')
				{
					if(col[board[j][i]-'1'] > 0)return false;
					else col[board[j][i]-'1']++;
				}
			}
		}

		for(int i = 0; i < 9; i+=3)
			for(int j = 0; j < 9; j+=3)
			{
				memset(row,0,sizeof(int)*9);
				for(int a = 0; a < 3; a++)
					for(int b= 0; b < 3; b++)
						if(board[i+a][j+b] != '.')
						{
							if(row[board[i+a][j+b]-'1']>0)return false;
							else row[board[i+a][j+b]-'1']++;
						}
			}
        return true;
    }

public boolean isValidSudoku(char[][] board) {
		boolean[] visited = new boolean[10];
		//row
		for(int i=0; i<9; i++) {
			Arrays.fill(visited, false);
			for(int j=0; j<9; j++) {
				if( !check(visited, board[i][j]) ) {
					return false;
				}
			}
		}
		//col
		for(int i=0; i<9; i++) {
			Arrays.fill(visited, false);
			for(int j=0; j<9; j++) {
				if( !check(visited, board[j][i]) ) {
					return false;
				}
			}
		}
		//sub matrix
		for(int i=0; i<9; i+=3) {
			for(int j=0; j<9; j+=3) {
				Arrays.fill(visited, false);
				for(int k=0; k<9; k++) {
					if( !check(visited, board[i+k/3][j+k%3]) ) {
						return false;
					}
				}
			}
		}
		return true;
    }
	
	private boolean check(boolean[] visited, char c) {
		if(c == '.') {
			return true;
		}
		int num = c - '0';
		if(num<1 || num>9 ||visited[num]) {
			return false;
		} else {
			visited[num] = true;
		}
		return true;
	}