【leetCode刷题日记】200. Number of Islands

class Solution {private:    vector<vector<bool>> isCounted;    int d[4][2] = {{0,1},{1,0},{0,-1},{-1,0}};//四方向移动    int r,c;    bool isLegal(int x,int y){        return 0<=x && x<r && 0<=y && y<c;    }    void dfs(vector<vector<char>>& grid,int i, int j){        isCounted[i][j] = true;        //cout<<i<<" "<<j<<endl;        for(int k=0;k<4;k++){            int newx = i + d[k][0];            int newy = j + d[k][1];            if(isLegal(newx,newy) && !isCounted[newx][newy] && grid[newx][newy] == '1'){                dfs(grid,newx,newy);            }        }        return;    }public:    int numIslands(vector<vector<char>>& grid) {        int res = 0;//岛屿数量        r = grid.size();//行数        if(r == 0) return 0;        c = grid[0].size();//列数        isCounted = vector<vector<bool>>(r,vector<bool>(c,false));        for(int i = 0;i < r; i++){            for(int j = 0;j < c;j++){                if(!isCounted[i][j] && grid[i][j] == '1'){                    //cout<<"a"<<endl;                    //floodfill,用dfs将周围岛屿全部标记                    dfs(grid,i,j);                    res++;                }            }        }        return res;    }};