Valid sudoku

题目：

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 '.'.

思路：做三个判断：行，列， block

代码：

 1 class Solution {
 2 public:
 3     bool isValidSudoku(vector<vector<char> > &board) {
 4      
 5         vector<vector<bool> > rows(9, vector<bool>(9, false));
 6         vector<vector<bool> > cols(9, vector<bool>(9, false));
 7         vector<vector<bool> > blocks(9, vector<bool>(9, false));
 8 
 9         for (int i = 0; i < 9; ++i) {
10             for (int j = 0; j < 9; ++j) {
11                 if (board[i][j] == '.') continue;
12                 int c = board[i][j] - '1';
13                 if (rows[i][c] || cols[j][c] || blocks[i - i % 3 + j / 3][c])
14                     return false;
15                 rows[i][c] = cols[j][c] = blocks[i - i % 3 + j / 3][c] = true;
16             }
17         }
18         return true;
19     }
20 };