River Crossing River Pirates Expert — Set 87

Expert River Crossing Puzzle #87

Title

Expert River Crossing Puzzle #87

Scenario

Pirate Treasure

Narrative

Three pirates and one treasure chest must cross a river. The rowboat holds 2 passengers (pirates or chest). If a pirate is alone with the chest and another pirate is on the other bank, he will steal it.

Entities

• {"id":"p1","name":"Pirate 1","icon":"\ud83c\udff4\u200d\u2620\ufe0f"}
• {"id":"p2","name":"Pirate 2","icon":"\ud83c\udff4\u200d\u2620\ufe0f"}
• {"id":"p3","name":"Pirate 3","icon":"\ud83c\udff4\u200d\u2620\ufe0f"}
• {"id":"t1","name":"Treasure Chest","icon":"\ud83d\udcb0"}

BoatCapacity

2

Constraints

• The boat holds at most 2.
• The chest cannot be left with only 1 pirate (he will take it).
• All three pirates must accompany the chest at journey's end.

Question

Describe a valid sequence of crossings that gets everyone to the other side without violating any constraint. What is the minimum number of trips required?

Solution

• {"trip":1,"direction":"\u2192","carrying":["Pirate 1","Pirate 2"],"leftBank":"P3,Chest","rightBank":"P1,P2","note":"2 pirates cross."}
• {"trip":2,"direction":"\u2190","carrying":["Pirate 1"],"leftBank":"P1,P3,Chest","rightBank":"P2","note":"P1 returns."}
• {"trip":3,"direction":"\u2192","carrying":["Pirate 1","Chest"],"leftBank":"P3","rightBank":"P1,P2,Chest","note":"P1 takes chest across."}
• {"trip":4,"direction":"\u2190","carrying":["Pirate 2"],"leftBank":"P2,P3","rightBank":"P1,Chest","note":"P2 returns."}
• {"trip":5,"direction":"\u2192","carrying":["Pirate 2","Pirate 3"],"leftBank":"","rightBank":"All","note":"P2 and P3 cross. Done!"}

MinimumTrips

5

Hint

No hints are provided for this difficulty. Find the full solution on your own.

PartialSolutionHint