[Oracle] LeetCode 37 Sudoku Solver

Write a program to solve a Sudoku puzzle by filling the empty cells.

A sudoku solution must satisfy all of the following rules:

• Each of the digits 1-9 must occur exactly once in each row.
• Each of the digits 1-9 must occur exactly once in each column.
• Each of the digits 1-9 must occur exactly once in each of the 9 3x3 sub-boxes of the grid.

The '.' character indicates empty cells.

Solution

对于每一个空缺的位置，我们需要遍历所有的数字进行 $check$

$check$ 的时候我们需要对于所在行，所在列，以及小九宫格进行检查，这里注意九宫格检查的写法

点击查看代码

class Solution {
private:
    bool check(char c, vector<vector<char>>& board, int row, int col){
        for(int i=0;i<9;i++){
            if(board[i][col]==c)return false;
            if(board[row][i]==c)return false;
            if(board[3*(row/3)+i/3][3*(col/3)+i%3]==c)return false;
        }
        return true;
    }
    
    bool dfs(vector<vector<char>>& board){
        int nr = board.size(), nc = board.size();
        for(int i=0;i<nr;i++){
            for(int j=0;j<nc;j++){
                if(board[i][j]=='.'){
                    for(char c = '1';c<='9';c++){
                        if(check(c,board,i,j)){
                            board[i][j]=c;
                            if(dfs(board))return true;
                            else board[i][j]='.';
                        }
                    }
                    return false;
                }
            }
        }
        return true;
    }
    
public:
    void solveSudoku(vector<vector<char>>& board) {
        dfs(board);
    }
};