River Crossing River Bridge Torch Hard — Set 100

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{
    "title": "Hard River Crossing Puzzle #100",
    "scenario": "Bridge & Torch",
    "narrative": "Four people must cross a rickety bridge at night with one torch. The bridge holds at most 2 people. Each pair crosses at the speed of the slower person. Minimize total crossing time.",
    "entities": [
        {
            "id": "p1",
            "name": "Person A (1 min)",
            "icon": "🏃"
        },
        {
            "id": "p2",
            "name": "Person B (2 min)",
            "icon": "🚶"
        },
        {
            "id": "p5",
            "name": "Person C (5 min)",
            "icon": "🧍"
        },
        {
            "id": "p8",
            "name": "Person D (8 min)",
            "icon": "🐢"
        }
    ],
    "boatCapacity": 2,
    "constraints": [
        "The bridge holds at most 2 people at once.",
        "The torch must be carried across and brought back — you cannot throw it.",
        "When two people cross together, they move at the slower person's speed.",
        "Crossing speeds: A=1 min, B=2 min, C=5 min, D=8 min."
    ],
    "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": "→",
            "carrying": [
                "A (1)",
                "B (2)"
            ],
            "leftBank": "C,D",
            "rightBank": "A,B",
            "note": "A and B cross together. Time: 2 min."
        },
        {
            "trip": 2,
            "direction": "←",
            "carrying": [
                "A (1)"
            ],
            "leftBank": "A,C,D",
            "rightBank": "B",
            "note": "A returns with torch. Time: 1 min."
        },
        {
            "trip": 3,
            "direction": "→",
            "carrying": [
                "C (5)",
                "D (8)"
            ],
            "leftBank": "A",
            "rightBank": "B,C,D",
            "note": "C and D cross. Time: 8 min."
        },
        {
            "trip": 4,
            "direction": "←",
            "carrying": [
                "B (2)"
            ],
            "leftBank": "A,B",
            "rightBank": "C,D",
            "note": "B returns with torch. Time: 2 min."
        },
        {
            "trip": 5,
            "direction": "→",
            "carrying": [
                "A (1)",
                "B (2)"
            ],
            "leftBank": "",
            "rightBank": "All",
            "note": "A and B cross. Time: 2 min. Total: 15 min."
        }
    ],
    "minimumTrips": 5,
    "hint": "The first 1 move(s) of the solution are shown below to help you start.",
    "partialSolutionHint": [
        {
            "trip": 1,
            "direction": "→",
            "carrying": [
                "A (1)",
                "B (2)"
            ],
            "leftBank": "C,D",
            "rightBank": "A,B",
            "note": "A and B cross together. Time: 2 min."
        }
    ],
    "_archetype": null,
    "_generatorId": null
}