All Rubik's cube positions can be solved in 20 moves or less; http://www.cube20.org/
What's one such position that requires 19 moves to solve, please give the faces, and the moves to solve.
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asked Nov 17, 2014 at 10:54
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2$\begingroup$ The page you link to actually gives such a position, the "Superflip" in the applet at the top of the page (skip to the end to see the position). More information is given in the "What are the Hardest Positions?" section. $\endgroup$– user251Commented Nov 17, 2014 at 11:00
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$\begingroup$ @Arthur Snap never even saw that! Hold on... $\endgroup$– warspykingCommented Nov 17, 2014 at 11:15
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$\begingroup$ "Other than the one given on the site" has now been added to the question $\endgroup$– warspykingCommented Nov 17, 2014 at 11:16
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1$\begingroup$ The site does also give a list of all known distance-20 states. $\endgroup$– user20Commented Nov 17, 2014 at 11:28
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5$\begingroup$ This question appears to be off-topic because it has many answers and link is available from the OP himself. $\endgroup$– Mohit JainCommented Nov 17, 2014 at 12:06
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2 Answers
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Given any position you know that has 20 moves (like the Superflip) just do one move towards the solution and you have a position that requires 19 moves.
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1$\begingroup$ To be more accurate, since the superflip is highly symmetrical: Take the superflip and make any move. $\endgroup$– BassCommented Oct 24, 2017 at 18:37
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Below sequence movement from a solved cube will make the position solvable in 19 moves
F U' F2 D' B U R' F' L D' R' U' L U B' D2 R' F U2
And the solution would be
Step 1: U2
Step 2: F'
Step 3: R
Step 4: D2
Step 5: B
Step 6: U'
Step 7: L'
Step 8: U
Step 9: R
Step10: D
Step11: L'
Step12: F
Step13: R
Step14: U'
Step15: B'
Step16: D
Step17: F2
Step18: U
Step19: F'
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$\begingroup$ Can you prove it requires 19 moves though? That is that no 18- moves solution exists? $\endgroup$ Commented Nov 17, 2014 at 15:29
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$\begingroup$ Yes, this is superflip config with one less twist. If this has a better solution, superflip would be solvable in fewer than 20 steps. $\endgroup$ Commented Nov 17, 2014 at 16:09
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1$\begingroup$ Ah, didn't realize this is superflip :) Roger that. $\endgroup$ Commented Nov 17, 2014 at 16:09