CPP Program for counting number of islands - a famous DFS question

Number_of_islands.cpp

@@ -0,0 +1,78 @@
+#include<bits/stdc++.h>
+using namespace std;
+
+// Given a grid consisting of '0's(Water) and '1's(Land). Find the number of islands.
+// An island is surrounded by water and is formed by connecting adjacent lands 
+// horizontally or vertically or diagonally i.e., in all 8 directions.
+
+
+class Solution
+{
+
+
+    void mark(vector<vector<char>> &matrix,int x,int y,int r,int c)
+    {
+        if(x<0 || x>=r || y<0 || y>=c || matrix[x][y]!='1')  
+            return;
+
+
+        matrix[x][y] = '2';
+
+
+        mark(matrix,x+1,y,r,c);  
+        mark(matrix,x,y+1,r,c);  
+        mark(matrix,x-1,y,r,c);  
+        mark(matrix,x,y-1,r,c); 
+        mark(matrix,x-1,y-1,r,c);  
+        mark(matrix,x+1,y+1,r,c);  
+        mark(matrix,x+1,y-1,r,c);  
+        mark(matrix,x-1,y+1,r,c); 
+
+    }
+    public:
+
+    int numIslands(vector<vector<char>>& grid) 
+    {
+
+        int row=grid.size();
+        if(row==0)    
+        return 0;
+        int col=grid[0].size();
+
+
+        int ans=0;
+        for(int i=0;i<row;++i)
+        {
+            for(int j=0;j<col;++j)
+            {
+                if(grid[i][j]=='1')
+                {
+                    mark(grid,i,j,row,col);
+                    ans++;
+                }
+            }
+        }
+        return ans;
+
+    }
+};
+
+
+int main(){
+	int tc;
+	cin >> tc;
+	while(tc--){
+		int n, m;
+		cin >> n >> m;
+		vector<vector<char>>grid(n, vector<char>(m, '#'));
+		for(int i = 0; i < n; i++){
+			for(int j = 0; j < m; j++){
+				cin >> grid[i][j];
+			}
+		}
+		Solution obj;
+		int ans = obj.numIslands(grid);
+		cout << ans <<'\n';
+	}
+	return 0;
+}