[LeetCode]Surrounded Regions

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

class Solution {

public:

    int dir[4][2] = {{0,1},{0,-1},{1,0},{-1,0}};

    void solveUtil(vector<vector<char> >& board, vector<vector<bool> >& visited, int ix, int iy, vector<pair<int,int> >& curPath, bool& isSurrounded)

    {

        int n = board.size();

        int m = board[0].size();

        queue<pair<int,int> > posQ;

        posQ.push(pair<int,int>(ix, iy));

        while(!posQ.empty())

        {

            int curX = posQ.front().first;

            int curY = posQ.front().second;

            posQ.pop();

            

            if(board[curX][curY] == 'O' && !visited[curX][curY])

            {

                curPath.push_back(pair<int,int>(curX, curY));

                visited[curX][curY] = true;

                for(int k = 0; k < 4; ++k)

                {

                    int newX = curX+dir[k][0];

                    int newY = curY+dir[k][1];

                    if(newX < 0 || newX >= n || newY < 0 || newY >= m) isSurrounded = false;

                    else if (!visited[newX][newY]) posQ.push(pair<int,int>(newX, newY));

                }

                    

            }

        }

        

    }

    void solve(vector<vector<char>> &board) {

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

        // DO NOT write int main() function

        int n = board.size();

        if(n == 0) return;

        int m = board[0].size();

        

        vector<vector<bool> > visited(n, vector<bool>(m, false));

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

        {

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

            {

                vector<pair<int, int> > curPath;

                bool isSurrounded = true;

                if(!visited[i][j]) solveUtil(board, visited, i, j, curPath, isSurrounded);

                if(isSurrounded)    

                {

                    for(int i = 0; i < curPath.size(); ++i) 

                        board[curPath[i].first][curPath[i].second] = 'X';

                }

            }

        }

        

    }

};