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.

class Solution {public:    void solveSudoku(vector<vector<char> > &board) {vector<short> row(9,0),col(9,0),grid(9,0);//出现了哪些数字for(int i=0;i<9;i++){for(int j=0;j<9;j++){if(board[i][j]!='.'){row[i] |= 1<<(board[i][j]-'1');col[j] |= 1<<(board[i][j]-'1');grid[3*(i/3)+j/3] |= 1<<(board[i][j]-'1');}}}//低9位求反short flag = pow(2,9)-1;for(int i=0;i<9;i++){row[i] ^= flag ;col[i] ^= flag ;grid[i] ^= flag;}bool isEnd=false;solve(board,row,col,grid,isEnd);}void solve(vector<vector<char>> &board,vector<short> &row,vector<short> &col,vector<short> &grid,bool &isEnd){    //forgot to end..    if(isEnd)        return;for(int i=0;i<9;i++)        {            for(int j=0;j<9;j++)            {                if(board[i][j]=='.')                {//尝试赋值short flag= row[i]&col[j]&grid[i/3*3+j/3];                    for(int k=0;flag!=0 && k<9;k++){if((flag & (1 << k)) !=0 ){board[i][j]=k+'1';row[i] ^= (1<<k);col[j] ^= (1<<k);grid[i/3*3+j/3] ^= (1<<k);solve(board,row,col,grid,isEnd);if(isEnd){//找到解后不回退    return;}//回退    board[i][j]='.';    row[i] ^= (1<<k);    col[j] ^= (1<<k);    grid[i/3*3+j/3] ^= (1<<k);}                    }return;                }            }        }        isEnd=true;    }};