LeetCode: Sudoku Solver

看了网上答案，发现一个很有趣的问题，check函数里形参board是传值时（即&board)速度很快，能过large，去掉这个&后就过不了large了，是不是因为没有传值的话每次需要复制这样耗了时间了呢

 1 class Solution {

 2 public:

 3     bool check(int x, int y, vector<vector<char>> &board) {

 4         bool flag[9] = {false};

 5         for (int i = 0; i < 9; i++) 

 6             if (board[x][i] != '.') 

 7                 if (!flag[board[x][i]-'1']) flag[board[x][i]-'1'] = true;

 8                 else return false;

 9         memset(flag, false, 9);

10         for (int i = 0; i < 9; i++) 

11             if (board[i][y] != '.')

12                 if (!flag[board[i][y]-'1']) flag[board[i][y]-'1'] = true;

13                 else return false;

14         memset(flag, false, 9);

15         int xx = x/3*3;

16         int yy = y/3*3;

17         for (int i = 0; i < 3; i++)

18             for (int j = 0; j < 3; j++) 

19                 if (board[xx+i][yy+j] != '.')

20                     if (!flag[board[xx+i][yy+j]-'1']) flag[board[xx+i][yy+j]-'1'] = true;

21                     else return false;

22         return true;

23     }

24     bool dfs(vector<vector<char>> &board) {

25         for (int i = 0; i < 9; i++) {

26             for (int j = 0; j < 9; j++) {

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

28                     for (char k = '1'; k <= '9'; k++) {

29                         board[i][j] = k;

30                         if (check(i, j, board) && dfs(board)) return true;

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

32                     }

33                     return false;

34                 }

35             }

36         }

37         return true;

38     }

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

40         // Start typing your C/C++ solution below

41         // DO NOT write int main() function

42         dfs(board);

43     }

44 };

 C#

 1 public class Solution {

 2     public void SolveSudoku(char[,] board) {

 3         dfs(board);

 4         

 5     }

 6     public bool dfs(char[,] board) {

 7         for (int i = 0; i < 9; i++) {

 8             for (int j = 0; j < 9; j++) {

 9                 if (board[i, j] == '.') {

10                     for (char k = '1'; k <= '9'; k++) {

11                         board[i, j] = k;

12                         if (check(i, j, board) && dfs(board)) return true;

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

14                     }

15                     return false;

16                 }

17             }

18         }

19         return true;

20     }

21     public bool check(int x, int y, char[,] board) {

22         bool[] flag = new bool[9];

23         for (int i = 0; i < 9; i++) {

24             if (board[x, i] != '.') {

25                 if (!flag[board[x, i] - '1']) flag[board[x, i] - '1'] = true;

26                 else return false;

27             }

28         }

29         flag = new bool[9];

30         for (int i = 0; i < 9; i++) 

31             if (board[i, y] != '.')

32                 if (!flag[board[i, y]-'1']) flag[board[i, y]-'1'] = true;

33                 else return false;

34         flag = new bool[9];

35         int xx = x/3*3;

36         int yy = y/3*3;

37         for (int i = 0; i < 3; i++)

38             for (int j = 0; j < 3; j++) 

39                 if (board[xx+i, yy+j] != '.')

40                     if (!flag[board[xx+i, yy+j]-'1']) flag[board[xx+i, yy+j]-'1'] = true;

41                     else return false;

42         return true;

43     }

44 }

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