[LeetCode] 36. Valid Sudoku

Posted 2020-09-10

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.

 

Note:
A valid Sudoku board (partially filled) is not necessarily solvable. Only the filled cells need to be validated.

 1 // From Discuss
 2 class Solution {
 3 public:
 4     bool isValidSudoku(vector<vector<char>>& board) {
 5         //used1: check each row
 6         //used2: check each column
 7         //used3: check each sub-boxes
 8         bool used1[9][9]={false}, used2[9][9]={false}, used3[9][9]={false};
 9         
10         for (int i = 0; i < board.size(); ++i){
11             for (int j = 0; j < board[i].size(); ++j){
12                 if (board[i][j] != ‘.‘){
13                     int num = board[i][j] - ‘0‘ - 1;
14                     int k = i / 3 * 3 + j / 3;
15                     if (used1[i][num] || used2[j][num] || used3[k][num]){
16                         return false;
17                     }else{
18                         used1[i][num] = used2[j][num] = used3[k][num] = true;
19                     }
20                 }
21             }
22         }
23         
24         return true;
25     }
26 };