On 02 Jan 03 at 09:52:12AM, artist google wrote: > > > Hi, > > > I have this puzzle. > > > Given N numbers, N>4, you have to sort the > > numbers. > > > The only operation permitted is you can rotate > > any > > > sequencial 4 numbers in reverse order. or you can > > > roate the entire list sequencially. > > > > > > How do u approach this?? > > > > > What is a reverse/sequential rotation ? > > > 1. you can compare numbers. > 2. rotate sequencial 4 numbers: > from.. 1 2 3 4 5 6 7 > to 1 2 6 5 4 3 7 > (ie.. 3 4 5 6 is rotated to 6 5 4 3) > 3. rotate entire sequence > from.. 1 2 6 5 4 3 7 > to 3 7 1 2 6 5 4
Is (3) correct? In (2), "rotations" appears to mean flipping the subsequence, but in (3), it appears to mean rotate in the sense I first interpreted it (cycling elements from one end to the other, without otherwise changing the order. Which of these is correct? a. both mean "flipping": 12 3456 7 -> 12 6543 7 1234567 -> 7654321 b. both mean "cycling:" 12 3456 7 -> 12 4563 7 1234567 -> 2345671 c. They mean different things as you have described above. In that case, it appears to be what I call "cycling", but you have shifted two elements. Is any number of shifts allowed whilst still being treated as an atomic operation? --- Is this a puzzle from some source you can put us onto for clarification, or did you make it up? Regards, Ian Boreham
