Surrounded Regions

Description：

Given a 2D board containing 'X' and 'O', capture all regions surrounded by 'X'.

A region is captured by flipping all 'O's into 'X's in that surrounded region.

For example,

X X X X
X O O X
X X O X
X O X X

 

After running your function, the board should be:

X X X X
X X X X
X X X X
X O X X

Code：

 1 struct vertex
 2 {
 3     int row;
 4     int col;
 5     vertex (int x, int y):row(x),col(y)
 6     {
 7         
 8     }
 9 };
10 
11   void BFSTraverse (vector< vector<char> >& board, int i, int j)
12   {//因为值被修改为'S'就说明该元素已被访问，所以本题中可以不用另外的变量记录访问状态
13             board[i][j] = 'S';
14             deque<vertex>m;
15             m.push_back( vertex(i,j) );
16             while ( !m.empty() )
17             {
18                    vertex v = m.front();
19                    m.pop_front();
20 
21                    int mRow = v.row-1;
22                    if ( mRow >=0 && board[mRow][v.col] == 'O')
23                     {//上面的元素
24                            board[mRow][v.col] = 'S';
25                            m.push_back( vertex(mRow, v.col) );
26                    }
27                    mRow = v.row+1;
28                    if ( mRow < board.size() && board[mRow][v.col] == 'O')
29                    {//下面的元素
30                            board[mRow][v.col] = 'S';
31                            m.push_back( vertex(mRow, v.col) );
32                    }
33                    int mCol = v.col - 1;
34                    if ( mCol >=0 && board[v.row][mCol] == 'O')
35                    {//左面的元素
36                            board[v.row][mCol] = 'S';
37                            m.push_back( vertex(v.row, mCol));
38                    }
39                     mCol = v.col + 1;
40                    if ( mCol < board[0].size()  && board[v.row][mCol] == 'O' )
41                    {//右面的元素
42                            board[v.row][mCol] = 'S';
43                            m.push_back( vertex(v.row, mCol));
44                    }
45            }
46   }
47     
48     void solve(vector< vector<char> >& board)
49     {
50         int row = board.size();
51         if ( row!=0 )
52         {
53             int col = board[0].size();
54             for (int j = 0; j < col; ++j)
55            {
56                 if ( board[0][j] == 'O')
57                     BFSTraverse (board, 0, j);
58                 if ( board[row-1][j] == 'O')
59                     BFSTraverse (board, row-1, j);
60            }
61            for (int i = 1;  i < row-1; ++i)
62            {
63                if ( board[i][0] == 'O')
64                     BFSTraverse (board, i, 0);
65                 if ( board[i][col-1] == 'O' )
66                     BFSTraverse (board, i, col-1);
67            }
68            
69            for (int  i = 0; i < row; ++i )
70            {
71                for ( int j = 0; j < col; ++j )
72                {
73                    if (board[i][j] == 'S')
74                         board[i][j] = 'O';
75                    else if (board[i][j] == 'O')
76                         board[i][j] = 'X';
77                    else
78                    ;
79                }
80            }//for
81         }//if
82     }

 

posted @ 2015-06-21 16:46  Rosanne  阅读(189)  评论(0)  编辑  收藏  举报