This was my first 4-hour heuristic competition and coding time was considerably the limiting factor. After 4 hours I was in 448th on the leaderboard. Continuing after the competition ended, I improved that to 247th on the extended leaderboard.

The final solution first calculated a fallback solution, which was the optimal possible solution using only “Move” and “Slide” actions.

The bulk of the 2s time limit was spent trying with blocks in a variety of locations. Each trial started by pre-selecting a random set of 7-14 move indexes & directions. The move indexes were limited to the first quarter of the length of the current best solution.

Then it set about moving from target to target, using A* to find the fastest route between the two. After making the relevant number of moves, it would place a block in the specified direction, provided that the block wasn’t out of bounds. (Each time a block was placed, pre-calculation of data for the A* heuristic and “Slide” distances were calculated to increase simulation speed.)

The best solution was submitted when the 2s time limit was near. Running with Cython allowed approximately 230 trials in the time limit. CPython only managed ~180 trials. However, the difference in overall score from switching to Cython was negligible.