15 February Geeks Island

class Solution{   
public:
    void dfs(vector<vector<int>> &mat,int i,int j,int n,int m,vector<vector<bool>> &visited){
        if(i<0 || i>=n || j<0 || j>=m  || visited[i][j])
            return;
        visited[i][j] = true;
        
        if(j+1 < m && mat[i][j+1] >= mat[i][j] && !visited[i][j+1]) // right
            dfs(mat,i,j+1,n,m,visited);
        if(i+1 < n && mat[i+1][j] >= mat[i][j] && !visited[i+1][j]) // down
            dfs(mat,i+1,j,n,m,visited);
        if(j-1 >= 0 && mat[i][j-1] >= mat[i][j] && !visited[i][j-1]) //left
            dfs(mat,i,j-1,n,m,visited);
        if(i-1 >= 0 && mat[i-1][j] >= mat[i][j] && !visited[i-1][j])// up
            dfs(mat,i-1,j,n,m,visited);
    }

    int water_flow(vector<vector<int>> &mat,int N,int M){
    // Write your code here.
        vector<vector<bool>> indian(N,vector<bool>(M,false));
        vector<vector<bool>> arabian(N,vector<bool>(M,false));
        
        for(int j=0;j<M;j++)
            dfs(mat,0,j,N,M,indian);
        for(int i=0;i<N;i++)
            dfs(mat,i,0,N,M,indian);
        for(int j=0;j<M;j++)
            dfs(mat,N-1,j,N,M,arabian);
        for(int i=0;i<N;i++)
            dfs(mat,i,M-1,N,M,arabian);
            
        int ans=0;
        for(int i=0;i<N;i++){
            for(int j=0;j<M;j++){
                if(indian[i][j] && arabian[i][j])
                    ans++;
            }
        }
        return ans;
    }
};