leetcode 37 解数独

解数独

 深度优先搜索方法：以下为没有经过剪枝的代码

class Solution {
public:
    bool col[9][10];
    bool row[9][10];
    bool box[9][10];
    void solveSudoku(vector<vector<char>>& board) {
        if(board.size()!=9 || board[0].size()!=9) return;
        
        for(int i=0;i<9;i++){
            fill(col[i],col[i]+10,false);
            fill(row[i],row[i]+10,false);
            fill(box[i],box[i]+10,false);
        }
        for(int i=0;i<9;i++){
            for(int j=0;j<9;j++){
                int k=i/3*3+j/3;
                if(board[i][j]=='.') continue;
                int n=board[i][j]-'0';
                row[i][n]=true,col[j][n]=true,box[k][n]=true;
            }
        }
        dfs(board,0,0);
    }
    bool dfs(vector<vector<char>>& board,int i,int j){
        if(i==9) return true;
        if(j>=9) return dfs(board,i+1,0);
        if(board[i][j]!='.') return dfs(board,i,j+1);
        int k=i/3*3+j/3;
        for(int n=1;n<=9;n++){
            if(row[i][n]==false && col[j][n]==false && box[k][n]==false){
                row[i][n]=true,col[j][n]=true,box[k][n]=true;board[i][j]=(char)('0'+n);
                if(dfs(board,i,j+1)) return true;
                row[i][n]=false,col[j][n]=false,box[k][n]=false;board[i][j]='.';
            }   
        }
        return false;
    }
};