虽然我代码跑的贼慢，但我觉得 还行。

class Solution {
public:
    int numIslands(vector<vector<char>>& grid) {
        int rows = grid.size();
        if(rows == 0)
        	return 0;
        int cols = grid[0].size();
        int count = 0;
        int xDirection[4] = {-1 , 0 ,1 ,0};
        int yDirection[4] = {0 , 1 , 0 , -1};
        queue<int> queueA;
        set<int> setA;

        for( int i = 0 ; i < rows ; i++)
        {
        	for(int j = 0 ; j < cols ; j++)
        	{
        		if(grid[i][j] == '1' && (setA.find(i*cols + j) == setA.end()))
        		{
	        		queueA.push(i);
	        		queueA.push(j);
	        		setA.insert(i*cols + j);
	        		while(!queueA.empty())
	        		{
	        			int x = queueA.front();
	        			queueA.pop();
	        			int y = queueA.front();
	        			queueA.pop();

	        			for(int k = 0 ; k < 4 ; k++)
	        			{
	        				int tempX = x + xDirection[k];
	        				int tempY = y + yDirection[k];

	        				if(tempY < 0 || tempY >= cols || tempX < 0 || tempX >= rows)
	        					continue;

	        				if(grid[tempX][tempY] == '1' && (setA.find(tempX*cols + tempY) == setA.end()))
	        				{
	        					queueA.push(tempX);
	        					queueA.push(tempY);
	        					setA.insert(tempX*cols + tempY);
	        				}
	        			}

        			}
        			count++;
        		}
        	}
        }
        return count;
    }
};