leetcode[37]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.

A sudoku puzzle...

 

...and its solution numbers marked in red.

#define NUM 9

class Solution {

public:

bool isValidij(vector<vector<char> > &board, int i, int j) 

{

    for (int k=0;k<NUM;k++)

    {

        if (k!=j)

        {

            if(board[i][k]==board[i][j])return false;

        }

        if (k!=i)

        {

            if(board[k][j]==board[i][j])return false;

        }

    }

    int a=i/3*3;

    int b=j/3*3;

    for (int ii=a;ii<a+3;ii++)

    {

        for (int jj=b;jj<b+3;jj++)

        {

            if(ii!=i&&jj!=j)

            {

                if (board[ii][jj]==board[i][j])return false;

            }

        }

    }

    return true;

}

bool solve(vector<vector<char> > &board) 

{

    for (int i=0;i<NUM;i++)

    {

        for (int j=0;j<NUM;j++)

        {

            if (board[i][j]=='.')

            {

                int k=1;

                for (;k<=NUM;k++)

                {

                    board[i][j]='0'+k;

                    if (isValidij(board,i,j))

                    {

                        if(solve(board))return true;

                    }

                    board[i][j]='.';

                }

                return false;

            }

        }

    }

    return true;

}

void solveSudoku(vector<vector<char> > &board) 

{

        solve(board);

}

};