LeetCode 37. Sudoku Solver 数独游戏，DFS应用

设置3个数组，  

两个二维数组行数组和 列数组，  用来判断该行或该列内， 该值是否可标记

一个三维数组group数组，用来标记某个组内该值是否可标记

然后用dfs去搜即可

注意如果是数字则直接进入下一层

记得设置退出标志

class Solution {
public:
    int endflag = 0,m,n; 
    vector<vector<int>> cflag,rflag;
    vector<vector<vector<int>>> gflag;
    void dfs(vector<vector<char>>& board, int i, int j){
        if(j == n){
            j=0;
            i++;
        }
        if(endflag == 1 || (i==m && j== 0)){
            endflag = 1;
            return ;
        }
        int k;
        if(board[i][j] != '.'){
        dfs(board, i, j+1);
    }        
        for(k = 1;k <= 9 && !endflag ;k++){
            if(board[i][j] == '.' && cflag[j][k] ==1 && rflag[i][k] ==1 && gflag[i/3][j/3][k] == 1){
                cflag[j][k] = rflag[i][k] = gflag[i/3][j/3][k]= 0;
                board[i][j] = k + '0';
                dfs(board,i,j+1);
                if(endflag == 1)
                    return ;
                cflag[j][k] = rflag[i][k] = gflag[i/3][j/3][k]= 1;
                board[i][j] = '.';
            }
        }
    }
                                                                                  
                                                                                  
    void solveSudoku(vector<vector<char>>& board) {
        m=board.size(),n=board[0].size();
        int i,j,num;
        vector<vector<int>> Cflag(m,vector<int>(10,1)),Rflag(m,vector<int>(10,1));
        vector< vector< vector<int> > > Gflag(m/3,vector<vector<int>>(n/3,vector<int>(10,1)));
        cflag = Cflag;rflag = Rflag;gflag = Gflag;
        for(i=0;i<m;i++){
            for(j=0;j<n;j++){
                num = board[i][j];
                if(num != '.'){
                    num = num - '0';
                    rflag[i][num] = cflag[j][num] = 0;
                    gflag[i/3][j/3][num]=0;
                }
            }
        }
        dfs(board, 0, 0);
    }
};