class Solution {
private:
    vector<pair<int,int>>directions{{0,1},{0,-1},{1,0},{-1,0}};
    int num;//岛屿个数
    int max = 0;
    int cur_max = 0;
public:
    int maxAreaOfIsland(vector<vector<int>>& grid) {
        int row=grid.size();//row行数
        int col=grid[0].size();//column列数
        for(int i=0;i<row;i++){
            for(int j=0;j<col;j++){
                if(grid[i][j] == 1){
                    num++;
                    dfs(grid,i,j);
                    if(max < cur_max){
                        max = cur_max;
                    }
                    cur_max = 0;
                }
            }
        }
        return max;//返回岛屿个数
    }
    void dfs(vector<vector<int>>&grid,int x,int y){
        if(!isarea(grid,x,y)){
            return;//如果坐标(x,y)超过网格范围，则直接返回
        }
        if(grid[x][y]!=1){
            return;//如果不是岛屿(1)则直接返回
        }
        grid[x][y]=0;//将格子标记为已遍历过
        cur_max++;
        for(auto dir:directions){
            int newx=x+dir.first,newy=y+dir.second;
            if(isarea(grid,newx,newy)){//在网格范围内(正常)
                dfs(grid,newx,newy);
            }
        }
    }
    bool isarea(vector<vector<int>>&grid,int x,int y){//判断点是否在网格内
        if(x>=0 && x<grid.size() && 0<=y && y<grid[0].size()){
            return true;
        }else{
            return false;
        }
    }
};