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.

 

分析：行、列、3x3 box 分布check

1 class Solution { 2     public: 3         bool m_used[9]; 4         bool isValidSudoku(const vector
     
      
       >& board) { 5  6             // check the row 7             for (int i = 0; i < 9; ++i) { 8                 fill(m_used, m_used + 9, false); 9                 for (int j = 0; j < 9; ++j)10                 {11                     if (!check(board[i][j]))12                         return false;13                     m_used[board[i][j] - '1'] = true;14                 }15             }16 17             // check the column18             for (int i = 0; i < 9; ++i) {19                 fill(m_used, m_used + 9, false);20                 for (int j = 0; j < 9; ++j)21                 {   22                     if (!check(board[j][i]))23                         return false;24                     m_used[board[j][i] - '1'] = true;25                 }   26             }   27 28             // check the 3x3 box29             for (int r = 0; r < 3; ++r)30                 for( int c = 0; c < 3; ++c)31                 {32                     fill(m_used, m_used + 9, false);33                     for (int i = r * 3; i < r * 3 + 3; ++i)34                         for (int j = c * 3; j < c * 3 + 3; ++j)35                         {36                             if (!check(board[i][j]))37                                 return false;38                             m_used[board[i][j] - '1'] = true;39                         }40                 }41         return true;42         }43         bool check(char ch) {44             if (ch == '.') return true;45             if (m_used[ch - '1'] == true)46                 return false;47             else48                 return true;49         }50 };