37. Sudoku Solver-蒲公英云

37. Sudoku Solver

小鱼儿 2023-07-06 09:59 77阅读 0赞

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

Empty cells are indicated by the character '.'.

format_png
A sudoku puzzle…

format_png 1
…and its solution numbers marked in red.

Note:

The given board contain only digits 1-9 and the character '.'.
You may assume that the given Sudoku puzzle will have a single unique solution.
The given board size is always 9x9.

题意：数独

class Solution {
public:
   bool isValidSudoku(vector<vector<char>>& board, int i,int j,int c) 
   {         
        for (int k = 0; k < 9; k++)
        {
            if (board[i][k] == c)
                return false;
            if (board[k][j] == c)
                return false;
        }
        int begin = (i / 3);
        int end = (j / 3);
        for (int k = begin * 3; k < (begin+1) * 3; k++)
        { 
            for (int s = end * 3; s < (end + 1) * 3; s++)
            {
                if (board[k][s] == c)
                    return false;
            }
        }
        return true;
    }
    bool Helper(vector<vector<char>>& board)
    {
        for (int i = 0; i < 9; i++)
        {
            for (int j = 0; j < 9; j++)
            {
                if (board[i][j] == '.')
                {
                    for (char c = '1'; c <= '9'; c++)
                    {                  
                        if (isValidSudoku(board, i, j, c))
                        {
                            board[i][j] = c;
                            if (Helper(board))
                            {
                                return true;
                            }
                            else
                            {
                                board[i][j] = '.';
                            }
                        }                   
                    }
                    return false;
                }
            }
        }
        return true;
    }
    void solveSudoku(vector<vector<char>>& board)
    {
        Helper(board);
    }
};