Leetcode Note: Valid Sudoku

Leetcode Note: Valid Sudoku

I. Description

Determine if a Sudoku is valid, according to: Sudoku Puzzles-The Rules:
Http://sudoku.com.au/TheRules.aspx.
The Sudoku board cocould be partially filled, where empty cells are filled with the character '.'.

The following figure: A partially filled sudoku which is valid.

Ii. Question Analysis

The Sudoku matrix can be summarized as follows: for each row, column, and3×3Are there any unique0~9Arrangement and combination. If the same element exists, the Sudoku matrix is invalid.

This is a simple question, that is, to traverse all elements of the Sudoku matrix and check whether each element meets the nature of Sudoku. To determine whether an element is in a row, a column, or a residential area, I define ~ 9. number of occurrencesmap, Use'1'，'2'，...，'9'As long as the storage object of a keyword is greater than 1, it indicates3×3There is a duplicate keyword in the jiugongge area of. In this way, the traversal can be used to determine whether the matrix is legal.

Iii. Sample Code

#include 
  
   #include 
   
    #include
    using namespace std;class Solution{public:    bool isValidSudoku(vector
     
       >& board)    {        map
      
        sudokuMap; for (int i = 0; i < 9; i++) { sudokuMap.clear(); for (int j = 0; j < 9; j++) { sudokuMap[board[i][j]]++; if ((board[i][j] != '.') && (sudokuMap[board[i][j]] > 1)) return false; } } for (int i = 0; i < 9; i++) { sudokuMap.clear(); for (int j = 0; j < 9; j++) { sudokuMap[board[j][i]]++; if ((board[j][i] != '.') && (sudokuMap[board[j][i]] > 1)) return false; } } for (int i = 0; i < 9; i += 3) { for (int j = 0; j < 9; j += 3) { sudokuMap.clear(); for (int k = i; k < i + 3; k++) { for (int l = j; l < j + 3; l++) { sudokuMap[board[k][l]]++; if ((board[k][l] != '.') && (sudokuMap[board[k][l]] > 1)) return false; } } } } return true; }};
      
     
   
  

The running result is as follows:

1. A correct Sudoku matrix:

2. An incorrect Sudoku matrix:

Iv. Summary

This question does not require any algorithm. You only need to design matrix operations and usemapUsed to store each row, column, or cell.1~9The number of times each number appears. If a Sudoku is found to be larger than one, the Sudoku is immediately denied. valid sudoku is determined only when the Sudoku matrix is traversed and meets the requirements.