Skyscraper Solver

This project aims to find a fast solution to the Skyscraper puzzle.

Skyscraper is a logic puzzle where you fill a grid with numbers representing building heights while following visibility constraints.

I discovered this puzzle in Sekai CTF 2026, the 67 puzzles.

Solution Approach

The solver uses row-based backtracking with candidate pre-filtering.

At each step, the algorithm:

1. Generates all row permutations and filters them using left and right clues.
2. Sorts rows by candidate count (fewest first) to reduce branching.
3. Tries one candidate row at a time and checks column uniqueness incrementally.
4. Backtracks on conflict; after all rows are placed, validates top and bottom clues.