Number of Islands

Grid

Current Cell

Scanning

Islands Found

DFS Stack

DFS Stack / BFS Queue

Empty

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Water (0)

Land (1)

Current

Visited

Python Code - DFS Approach

                for i in range(rows):
            
                    for j in range(cols):
            
                        if grid[i][j] == "1" and not visited[i][j]:
            
                            islands += 1
            
                            dfs(i, j) # mark all connected land
            
                def dfs(i, j):
            
                    visited[i][j] = True
            
                    for di, dj in [(-1,0),(0,1),(1,0),(0,-1)]:
            
                        if valid(i+di, j+dj) and not visited:
            
                            dfs(i+di, j+dj)