132_leetcode_Sudoku Solver

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

1:採用遞歸；2:檢測當前空cell中放置的字符是不是滿足題意，如果不滿足，放置其它字符或者回朔；

    bool isValidSudokuCore(vector<vector<char> > &board, int curX, int curY)
    {
        for(int i = 0; i < (int)board.size(); i++)
        {
            if(i != curX && board[i][curY] !='.' && board[i][curY] == board[curX][curY])
            {
                return false;
            }
        }
        
        for(int i = 0; i < (int)board[0].size(); i++)
        {
            if(i != curY && board[curX][i] != '.' && board[curX][i] == board[curX][curY])
            {
                return false;
            }
        }
        
        int rows = curX / 3;
        int columns = curY / 3;
        
        for(int i = 0; i < 3; i++)
        {
            for(int j = 0; j < 3; j++)
            {
                if((rows * 3 + i != curX || columns * 3 + j != curY) && board[rows * 3 + i][columns * 3 + j] != '.' && board[rows * 3 + i][columns * 3 + j] == board[curX][curY])
                {
                    return false;
                }
            }
        }
        
        return true;
    }
    
    void solveSudoku(vector<vector<char> > &board)
    {
        solveSudokuCore(board);
    }
    
    bool solveSudokuCore(vector<vector<char> > &board)
    {
        for(int i = 0; i < 9; i++)
        {
            for(int j = 0; j < 9; j++)
            {
                if(board[i][j] == '.')
                {
                    bool flag = false;
                    for(int k = 1; k <= 9; k++)
                    {
                        board[i][j] = k + '0';
                        
                        flag = isValidSudokuCore(board, i, j) && solveSudokuCore(board);
                        
                        if(flag)
                        {
                            return true;
                        }
                    }
                    if(flag == false)
                    {
                        board[i][j] = '.';
                        return false;
                    }
                }
            }
        }
        return true;
    }