36. Valid Sudoku


Determine if a 9x9 Sudoku board is valid. Only the filled cells need to be validated according to the following rules:

  1. Each row must contain the digits 1-9 without repetition.
  2. Each column must contain the digits 1-9 without repetition.
  3. Each of the 9 3x3 sub-boxes of the grid must contain the digits 1-9 without repetition.


A partially filled sudoku which is valid.

The Sudoku board could be partially filled, where empty cells are filled with the character '.'.

Example 1:

Input:
[
  ["5","3",".",".","7",".",".",".","."],
  ["6",".",".","1","9","5",".",".","."],
  [".","9","8",".",".",".",".","6","."],
  ["8",".",".",".","6",".",".",".","3"],
  ["4",".",".","8",".","3",".",".","1"],
  ["7",".",".",".","2",".",".",".","6"],
  [".","6",".",".",".",".","2","8","."],
  [".",".",".","4","1","9",".",".","5"],
  [".",".",".",".","8",".",".","7","9"]
]
Output: true

Example 2:

Input:
[
  ["8","3",".",".","7",".",".",".","."],
  ["6",".",".","1","9","5",".",".","."],
  [".","9","8",".",".",".",".","6","."],
  ["8",".",".",".","6",".",".",".","3"],
  ["4",".",".","8",".","3",".",".","1"],
  ["7",".",".",".","2",".",".",".","6"],
  [".","6",".",".",".",".","2","8","."],
  [".",".",".","4","1","9",".",".","5"],
  [".",".",".",".","8",".",".","7","9"]
]
Output: false
Explanation: Same as Example 1, except with the 5 in the top left corner being 
    modified to 8. Since there are two 8's in the top left 3x3 sub-box, it is invalid.

Note:

  • A Sudoku board (partially filled) could be valid but is not necessarily solvable.
  • Only the filled cells need to be validated according to the mentioned rules.
  • The given board contain only digits 1-9 and the character '.'.
  • The given board size is always 9x9.

 

 1 class Solution {
 2 public:
 3     bool isValidSudoku(vector<vector<char>>& board) 
 4     {
 5         for(int i = 0;i<9;i++)//rows
 6         { 
 7             set<char> myset;
 8             for(int j = 0;j<9;j++){
 9                 if(board[i][j] == '.') continue;
10                 if(myset.find(board[i][j])==myset.end())
11                     myset.insert(board[i][j]);
12             else
13                 return false;
14             }
15         }
16         
17         for(int i = 0;i<9;i++)//cols
18         { 
19             set<char> myset;
20             for(int j = 0;j<9;j++){
21                 if(board[j][i] == '.') continue;
22                 if(myset.find(board[j][i])==myset.end())
23                     myset.insert(board[j][i]);
24             else
25                 return false;
26             }
27         }    
28         
29         for(int sub_i = 0;sub_i < 3;sub_i++)//sub-box
30             for(int sub_j = 0 ;sub_j < 3; sub_j++)
31             { 
32                 set<char> myset;
33                 for(int i = 0;i<3;i++)
34                     for(int j =0;j<3;j++)
35                     {
36                     
37                     if(board[sub_i*3+i][sub_j*3+j] == '.') continue;
38                     if(myset.find(board[sub_i*3+i][sub_j*3+j])==myset.end())
39                         myset.insert(board[sub_i*3+i][sub_j*3+j]);
40                     else
41                         return false;
42                     }
43             }
44                
45         return true;   
46         
47     }
48    
49 };

 

posted @ 2018-12-24 15:18  乐乐章  阅读(159)  评论(0)  编辑  收藏  举报