Philosopher's Stone Solution #4

This is the shorthand I'll be using to discuss the problem:

1. Each wine has one poison immediately to the left.
2. The potions at either end are different, neither one is the ahead potion
3. The potions in positions 2 and 6 are both wines.
4. Two visually different potions do not contain poison (though we don't know their positions)
5. Knowledge of the position of the two non-poison potions gives enough information to deduce uniquely the positions of the ahead and back potions. (Hermione solved it.)

This is by far the simplest problem: Using clues one two and three, we get the following two possible sequences:

Just by inspection, we see that the only way to tell which of these two possibilities is the solution is if the ahead potion is the dwarf or giant potion. Since the dwarf and giant potions are not poison, it's location in position 3 or 4 indicates the ahead potion.

Since Hermione solved the problem, the ahead potion must be the dwarf or giant.

Here's Hermione's solution:

"Got it," she said. "The smallest bottle will get us through the black fire -- towards the Stone."

Harry looked at the tiny bottle.

"There's only enough there for one of us," he said. "That's hardly one swallow."

They looked at each other.

"Which one will get you back through the purple flames?"

Hermione pointed at a rounded bottle at the right end of the line.

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Email: dave@tenletters.com