Count connected components in a binary grid
Company: Crowdstrike
Role: Software Engineer
Category: Coding & Algorithms
Difficulty: medium
Interview Round: Onsite
You are given an `m x n` grid of characters `'0'` and `'1'`:
- `'1'` represents land
- `'0'` represents water
Two land cells are connected if they share an edge (4-directional adjacency: up/down/left/right).
**Task**: Return the number of connected land components ("islands").
### Input
- `grid`: `m x n` matrix of characters `'0'`/`'1'`
### Output
- An integer: the number of islands
### Constraints
- `1 <= m, n <= 300`
- `grid[i][j] ∈ {'0','1'}`
### Example
Input:
```
1 1 0 0
1 0 0 1
0 0 1 1
```
Output:
```
3
```
Quick Answer: This question evaluates understanding of graph traversal and connected-components detection on a 2D grid, measuring the ability to model grid cells as nodes with four-directional adjacency and reason about connectivity.
Return the number of 4-directionally connected components of land cells "1" in a grid of "0"/"1" characters.
Constraints
- Use 4-directional adjacency
Examples
Input: ([['1', '1', '0', '0'], ['1', '0', '0', '1'], ['0', '0', '1', '1']],)
Expected Output: 2
Input: ([['0']],)
Expected Output: 0
Input: ([['1', '1'], ['1', '1']],)
Expected Output: 1
Hints
- DFS or BFS from each unseen land cell.