leetcode—sudoku solver

1.题目描述

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.

 

2.解法分析

class Solution
{
public:
    bool isValid(vector<vector<char> > &board, int x, int y)
    {
        int i, j;
        for (i = 0; i < 9; i++)
            if (i != x && board[i][y] == board[x][y])
                return false;
        for (j = 0; j < 9; j++)
            if (j != y && board[x][j] == board[x][y])
                return false;
        for (i = 3 * (x / 3); i < 3 * (x / 3 + 1); i++)
            for (j = 3 * (y / 3); j < 3 * (y / 3 + 1); j++)
                if (i != x && j != y && board[i][j] == board[x][y])
                    return false;
        return true;
    }
    
    bool solveSudoku(vector<vector<char>> &board)
    {
        for(int y=0;y<9;++y)
        {
            for(int x=0;x<9;++x)
            {
                if(board[y][x]=='.')
                {
                    for(int i=1;i<=9;++i)
                    {
                        board[y][x]='0'+i;
                        if(isValid(board,y,x))
                        {
                            // if(x==8)if(mySolveSudoku(board,sh+1))return true;
                              if(solveSudoku(board))return true;
                        }
                        
                        board[y][x]='.';
                    }
                    
                    return false;
                }
            }
        }
        
        return true;
    }
};