## Find Number of Islands

```Given a 2d grid map of `'1'`s (land) and `'0'`s (water), count the
number of islands. An island is surrounded by water and is
formed by connecting adjacent lands horizontally or vertically.
You may assume all four edges of the grid are all surrounded by water.```

#### Code:

```class Solution {
void mark_current_island(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')  //Boundary case for matrix
return;

//Mark current cell as visited
matrix[x][y] = '2';

//Make recursive call in all 4 adjacent directions
mark_current_island(matrix,x+1,y,r,c);  //DOWN
mark_current_island(matrix,x,y+1,r,c);  //RIGHT
mark_current_island(matrix,x-1,y,r,c);  //TOP
mark_current_island(matrix,x,y-1,r,c);  //LEFT
}
public:
int numIslands(vector<vector<char>>& grid) {

//For FAST I/O
ios_base::sync_with_stdio(false);
cin.tie(NULL);

int rows = grid.size();
if(rows==0)     //Empty grid boundary case
return 0;
int cols = grid[0].size();

//Iterate for all cells of the array
int no_of_islands = 0;
for(int i=0;i<rows;++i)
{
for(int j=0;j<cols;++j)
{
if(grid[i][j]=='1')
{
mark_current_island(grid,i,j,rows,cols);
no_of_islands += 1;
}
}
}
return no_of_islands;
}
};```