Leetcode: Sudoku Solver

最新推荐文章于 2025-07-29 09:07:56 发布

carlosten

最新推荐文章于 2025-07-29 09:07:56 发布

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分类专栏： Leetcode 文章标签： algorithm 面试

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本文介绍了一种通过编程解决数独谜题的方法，包括验证规则、递归求解以及实现完整的数独求解算法。

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

Empty cells are indicated by the character '.'.

You may assume that there will be only one unique solution.

A sudoku puzzle...

...and its solution numbers marked in red.

c++:

class Solution {
public:
    bool isvalid(int m, int n, vector<vector<char> > &board)
    {
        int i,j;
        for(i = 0;i < 9;i ++)
        {
            if(i != m && board[i][n] == board[m][n])
            {
                return false;
            }
        }
        for(j = 0;j < 9;j ++)
        {
            if(j != n && board[m][j] == board[m][n])
            {
                return false;
            }
        }
        for(i = (m/3)*3;i < (m/3)*3 + 3;i ++)
        {
            for(j = (n/3)*3;j < (n/3)*3 + 3;j ++)
            {
                if((i != m || j != n) && board[i][j] == board[m][n])
                {
                    return false;
                }
            }
        }
        return true;
    }
    bool solveSudokuHelper(vector<vector<char> > &board)
    {
        int i,j,k;
        for(i = 0;i < 9;i ++)
        {
            for(j = 0;j < 9;j ++)
            {
                if('.' == board[i][j])
                {
                    for(k = 1;k <= 9;k ++)
                    {
                        board[i][j] = '0' + k;
                        if(isvalid(i,j,board))
                        {
                            if(solveSudokuHelper(board))
                            {
                                return true;
                            }
                        }
                        board[i][j] = '.';
                    }
                    return false;
                }
            }
        }
        return true;
    }
    void solveSudoku(vector<vector<char> > &board) {
        solveSudokuHelper(board);
    }
};