19 August "Problem of the Day" Answer

                                                                   GeeksforGeeks
                                                           
The Question is :- "Unit Area of largest region of 1's"
Answer :-

class Solution
{
    public:
   int m,n ;
    int dxy[8][2] = {{1,0} , {1,1} , {0,1} , {-1,1} , {-1,0} , {-1,-1} , {0,-1} , {1,-1}} ;
    bool valid(int x, int y){
        return ((x>=0) && (y>=0) && (x<m) && (y<n)) ;
    }
    int bfs(int a , int b , vector<vector<int>>& grid){
       queue<pair<int , int>> q ;
       int cnt = 0 ;
       q.push({a,b}) ;
       grid[a][b] = 0 ; 
       while(!q.empty()){
           pair<int , int> top = q.front() ;
           a = top.first ;
           b = top.second ;
           q.pop(); 
           cnt++ ;
           for(int i=0;i<8;i++){
               int x = a + dxy[i][0] ; 
               int y = b + dxy[i][1] ; 
               if(valid(x,y) && (grid[x][y]==1)){
                   q.push({x,y}) ;
                   grid[x][y] = 0; 
               }
           }
       }
       return cnt ; 
    } 
    int findMaxArea(vector<vector<int>>& grid) {
        m = grid.size() ;
        n = grid[0].size() ;
        int ans = 0 ; 
        for(int i=0;i<m;i++){
            for(int j=0;j<n;j++){
                if(grid[i][j]==1){
                    ans = max(ans , bfs(i,j,grid)) ; 
                }
            }
        }
        return ans ; 
    }
};

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