Solution to LeetCode Problems: Valid Sudoku

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.

Thoughts:
Mark every used number in a row, column or block. When a re-marking occurs, return false. Note the method used to calculate the block ID using row and column indices.

Solution:

1. // ⑨ ばか
2. #define BAKA 9  
3.   
4. class Solution {  
5. public:  
6.     bool isValidSudoku(vector<vector<char> > &board) {  
7.         array<bool, BAKA> row[BAKA];  
8.         array<bool, BAKA> col[BAKA];  
9.         array<bool, BAKA> box[BAKA];  
10.   
11.         // as standard C array  
12.         // the variables are not initialized...  
13.         for(auto r = 0; r < BAKA; ++r)  
14.             for(auto c = 0; c < BAKA; ++c)  
15.                 row[r][c] = col[r][c] = box[r][c] = false;  
16.   
17.         for(auto r = 0; r < BAKA; ++r)  
18.             for(auto c = 0; c < BAKA; ++c)  
19.             {  
20.                 char ch=board[r][c];  
21.                 if (ch == '.')  
22.                     continue;   // blank, no effect  
23.                   
24.                 ch -= '1';  
25.                   
26.                 if (row[r][ch])  
27.                     return false;  
28.                 row[r][ch] = true;  
29.                   
30.                 if (col[c][ch])  
31.                     return false;  
32.                 col[c][ch] = true;  
33.                   
34.                 if (box[r / 3 * 3 + c / 3][ch])  
35.                     return false;  
36.                 box[r / 3 * 3 + c / 3][ch] = true;  
37.             }  
38.               
39.         return true;  
40.     }  
41. };