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Jumping Frogs Puzzle


JumpingFrogsPuzzle

The jumping frogs puzzle is a puzzle in which stacks of counters on a finite row of equally spaced positions are combined by jumps. A move carries an entire stack of k counters exactly k positions to the left or right, landing on another occupied position in the row and combining the two stacks. Empty positions remain in the row and count toward the jump distance. The goal is to combine all counters into a single stack.

The basic problem starts with a single counter at each of n positions, where n>=1 is an integer. All counters can be combined at either endpoint in exactly n-1 moves (Woll 2017, p. 2).

This follows by mathematical induction. The case n=1 requires no moves. Suppose that the result holds for n positions. For a row of n+1 positions, first combine the n rightmost counters at the right endpoint by the induction hypothesis. That stack contains n counters and is exactly n positions from the remaining counter at the left endpoint. Jumping the stack left combines all n+1 counters. Interchanging left and right gives the other endpoint. Finally, every move reduces the number of occupied positions by exactly one, which forces the total to be n-1.


See also

Puzzle

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References

Numberphile. "Frog Jumping." Featuring G. Hamilton. Feb. 23, 2017. https://www.youtube.com/watch?v=X3HDnrehyDM.Woll, C. "Jumping Frogs-Challenge #2." Feb. 2017. https://mathpickle.com/wp-content/uploads/2017/03/Jumping_Frogs___Challenge__2.pdf.

Cite this as:

Weisstein, Eric W. "Jumping Frogs Puzzle." From MathWorld--A Wolfram Resource. https://mathworld.wolfram.com/JumpingFrogsPuzzle.html

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