LeetCode 130 Surrounded Regions

题目 LeetCode 130

题解：

使用并查集解决
AC代码（c++）

class Solution {
public:
    int father[100005];
    int pos[1005][1005];
    void solve(vector<vector<char>>& board) {
        
        memset(tag,0,sizeof(tag));
        for(int i=0;i<=100000;i++)
		        father[i]=i;

        int p = 0;
        for(int i=0;i<board.size();i++)
        {
            for(int j=0;j<board[i].size();j++)
            {
                 if(board[i][j]=='O')
                 {
                    pos[i][j] = ++p;
         
                    if(i==board.size()-1||j==board[i].size()-1||i==0||j==0)
                    {
                        father[p] = 0;
                    }
                 }
            }
        }
        
        for(int i=0;i<board.size();i++)
        {
            for(int j=0;j<board[i].size();j++)
            {
                if(board[i][j]=='O')
                {
                    if(j-1>=0&&board[i][j-1] == 'O')
                    {
                        join(i,j,i,j-1);
                    }
                    if(i-1>=0&&board[i-1][j]=='O')
                    {
                        join(i,j,i-1,j);
                    }
                }
            }
        }
        
        for(int i=0;i<board.size();i++)
        {
            for(int j=0;j<board[i].size();j++)
            {
                if(board[i][j]=='O')
                {
                    find(pos[i][j]);
                    if(father[pos[i][j]]!=0)
                        board[i][j] = 'X';
                }
            }
        }
 
    }
    
    void join(int i1,int j1,int i2,int j2)
    {
        int f1 = find(pos[i1][j1]);
        int f2 = find(pos[i2][j2]);
        if(f1!=f2)
        {
            if(f1==0) father[f2] = f1;
            else if(f2==0) father[f1] = f2;
            else father[f2] =f1;
        }
    }
    
    int find(int x)
    {
        if(x!=father[x])
            father[x] = find(father[x]);
        return father[x];
    }
    
    
};