leetcode---Sudoku Solver---深搜

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.

class Solution {
public:
    bool isValidSudoku(vector<vector<char>>& board) 
    {
        int cnt[10];
        for(int i=0; i<9; i++) //每一行
        {
            memset(cnt, 0, sizeof(cnt));
            for(int j=0; j<9; j++)
            {
                if(board[i][j] != '.')
                {
                    cnt[board[i][j]-'0']++;
                    if(cnt[board[i][j]-'0'] > 1)
                        return false;
                }
            }
        }

        for(int i=0; i<9; i++) //每一列
        {
            memset(cnt, 0, sizeof(cnt));
            for(int j=0; j<9; j++)
            {
                if(board[j][i] != '.')
                {
                    cnt[board[j][i]-'0']++;
                    if(cnt[board[j][i]-'0'] > 1)
                        return false;
                }
            }
        }

        for(int i=0; i<9; i+=3) //每个宫
        {
            for(int j=0; j<9; j+=3)
            {
                memset(cnt, 0, sizeof(cnt));
                for(int a=i; a3; a++)
                {
                    for(int b=j; b3; b++)
                    {
                        if(board[a][b] != '.')
                        {
                            cnt[board[a][b]-'0']++;
                            if(cnt[board[a][b]-'0'] > 1)
                                return false;
                        }
                    }
                }
            }
        }

        return true;
    }

    bool dfs(vector<vector<char>>& board, int depth)
    {
        if(depth == 81)
        {
            if(isValidSudoku(board))
                return true;
            return false;
        }
        int x = depth / 9;
        int y = depth % 9;
        if(board[x][y] == '.')
        {
            for(int i=1; i<10; i++)
            {
                board[x][y] = i + '0';
                if(isValidSudoku(board))
                    if(dfs(board, depth+1))
                        return true;
                board[x][y] = '.';
            }
        }
        else
            if(dfs(board, depth+1))
                return true;
        return false;
    }

    void solveSudoku(vector<vector<char>>& board) 
    {
        dfs(board, 0);
    }
};