Clockwork Guardian | Coding

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🕰️ Clockwork Guardian — Write-Up | Cyber Apocalypse 2025

Details
URL [Hack The Box :: Clockwork Guardian
Difficulty Easy
Team Rank 541 / 8129
CTF Date 26 Mar, 13:00

📖 Challenge Summary

The Clockwork Sentinels defending Eldoria’s Skywatch Spire have gone rogue! You must navigate through the spire, avoiding hostile sentinels (1) and finding the safest path to the exit ('E'), starting from (0, 0).

🧠 Problem Rules

You are given a 2D grid where:

  • 0 = safe cell
  • 1 = hostile sentinel (blocked)
  • 'E' = exit
  • Start point is always (0, 0)

You can move:

  • Up
  • Down
  • Left
  • Right (no diagonals)

The goal is to find the shortest path from the start to the exit.

🧭 Strategy

This appears to be a shortest path problem on a grid — ideal for Breadth-First Search (BFS):

  • BFS guarantees the shortest path in unweighted graphs (like grids).
  • We enqueue each step with the running distance.
  • If we find 'E', we immediately return the current distance.

Edge cases handled:

  • Start cell is a 1 → no valid path.
  • 'E' must be treated as walkable.
  • Output must be only the path length or "Code is incorrect!" if unreachable.

🔮 Final Challenge Input

from collections import deque

# Read grid input (e.g., via copy-paste or platform input box)
grid = eval(input())

def bfs(grid):
    rows, cols = len(grid), len(grid[0])
    visited = [[False]*cols for _ in range(rows)]
    directions = [(-1,0), (1,0), (0,-1), (0,1)]

    if grid[0][0] == 1:
        print("Code is incorrect!")
        return

    queue = deque()
    queue.append((0, 0, 0))  # (row, col, distance)
    visited[0][0] = True

    while queue:
        r, c, dist = queue.popleft()

        if grid[r][c] == 'E':
            print(dist)
            return

        for dr, dc in directions:
            nr, nc = r + dr, c + dc
            if 0 <= nr < rows and 0 <= nc < cols:
                cell = grid[nr][nc]
                if not visited[nr][nc] and (cell == 0 or cell == 'E'):
                    visited[nr][nc] = True
                    queue.append((nr, nc, dist + 1))

    print("Code is incorrect!")

bfs(grid)

🧪 Example

Input:

[
    [0, 0, 1, 0, 0, 1],
    [0, 0, 0, 0, 0, 0],
    [0, 0, 0, 0, 0, 0],
    [0, 0, 1, 1, 0, 'E']
]

Output:

8

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