dfs-count-islands

grid = [
    ["1","1","0","0","0"],
    ["1","1","0","0","0"],
    ["0","0","1","0","0"],
    ["0","0","0","1","1"]
]


def visit_neighbours(i,j,grid,visited):
    r=len(grid)
    c=len(grid[0])

    if i<0 or j<0 or i>=r or j>=c or grid[i][j] == "0" or visited[i][j]: return
    visited[i][j]=True
    visit_neighbours(i,j+1,grid,visited)
    visit_neighbours(i+1,j,grid,visited)
    visit_neighbours(i,j-1,grid,visited)
    visit_neighbours(i-1,j,grid,visited)
    

def numIsLands(grid):
    if not grid: return 0
    
    r=len(grid)
    c=len(grid[0])
    
    visited = [[False for _ in range(c)] for _ in range(r)]
    islandscount = 0
    
    for i in range(r):
        for j in range(c):
            if grid[i][j] == "1" and not visited[i][j]:
                islandscount += 1
                visit_neighbours(i,j,grid,visited)
                
    return islandscount
    
print(numIsLands(grid))