695. Max Area of Island

 static int wing=[]()
 {
     std::ios::sync_with_stdio(false);
     cin.tie(NULL);
     return ;
 }();

 class Solution
 {
 public:
     int maxAreaOfIsland(vector<vector<int>>& grid)
     {
         int x=grid.size();
         int y=grid[].size();
         int res=;
         for(int i=;i<x;i++)
         {
             for(int j=;j<y;j++)
             {
                 res=max(res,countarea(grid,i,j));
             }
         }
         return res;
     }

     int countarea(vector<vector<int>> &grid,int i,int j)
     {
         int szx=grid.size();
         int szy=grid[].size();
         int count=;
         if(grid[i][j]==)
         {
             count++;
             grid[i][j]=;
             if(valid(i-,j,szx,szy)) count+=countarea(grid,i-,j);
             if(valid(i,j-,szx,szy)) count+=countarea(grid,i,j-);
             if(valid(i+,j,szx,szy)) count+=countarea(grid,i+,j);
             if(valid(i,j+,szx,szy)) count+=countarea(grid,i,j+);
             return count;
         }
         return ;
     }

     bool valid(int i,int j,int szx,int szy)
     {
         return i>=&&i<szx&&j>=&&j<=szy;
     }

 };

递归，问题不大