# Rook River (Chess Sliding Puzzle)

The absent-minded king has gotten himself lost. Help him return to his palace on h8 using as few moves as possible.

Only legal chess moves are allowed. Pawns are not promoted on the final rank.

You can post your solutions in quasi-algebraic notation. For example, moving the rook from e7 to e8 can be notated as Re7e8. Or you can post them as animations.

(Click on the image for a virtual board.)

The current best solution is by Arthelais at 70 moves.

Credit for the name of this puzzle goes to Dr Xorile.

• This... looks... fun... Commented Nov 28, 2016 at 5:34
• Can the pawns move diagonally as they do when capturing a piece?
– Sid
Commented Nov 28, 2016 at 7:25
• @Sid, the pawns cannot move diagonally because there is nothing to capture. Commented Nov 28, 2016 at 7:57
• +1 for the combo [chess] [sliding-blocks] and because it looks more impressive than the Ugren problem I posed & tagged with this combo. Commented Nov 28, 2016 at 8:20
• @RosieF, yours is also a great puzzle that I missed. For any others, who may also have missed it, her's the link: help black slide the blocks to solve this chess problem Commented Nov 28, 2016 at 19:34

Here's a solution (at least the upper bound of 125 moves). I've outlined it, to emphasize the key logic, and created an animation to show the whole solution):

Get the knight from c8 to d1 (moving the rooks on d&e); Also get the Bishop from f8 to e1; get the bishop from b8 to b2 moving the pawns up); Na2c3 (recently vacated by the bishop); Ka1a2; Bb2a1; Ka2b2; Nc3a2; Kb2c3; Nd1b2. At this point your king is ready to plunge into the Rook River.
Get the king out to d3; push the pawn c2c3; Rd2c2; clear the rooks to move the Nb2d1, filling in the gap with the rooks. Send the Knight up the river d1e3d5e7; clear the Rook at f8; Nh7f8; Bg8h7;Ne7g8; Bring the King up the river and replace the Knight on f8; Ng8e7; Kf8g8; f7f8; Nh8f7; Kg8h8

• "Rook River" is a fantastic name for this puzzle! I would rename it if you'd be so kind as to lend me the phrase? (Of course I would attribute it to you in the body of the puzzle.) But if you don't want to, that's fine too! Commented Nov 28, 2016 at 13:13
• Of course you can! Commented Nov 28, 2016 at 14:57
• How do you replace the bishops on f8 and g8 with knights?
– Sid
Commented Nov 28, 2016 at 14:59
• There is a bishop at f8. Rd2d3- Did you mean Rd2-c2?
– Sid
Commented Nov 28, 2016 at 15:27
• See italicized text. I got the Bishop down to e1, replacing it with a rook Commented Nov 28, 2016 at 15:32

Using Dr Xorile's answer as a base here is an improved solution:

It uses a total of $91$ moves.

Each move is listed below as the square from which to move a piece

  1. e7;  2. c8;  3. d8;  4. d7;  5. d6;  6. d5;  7. e7;  8. f8;  9. e8; 10. d8;
11. c8; 12. c7; 13. b8; 14. b7; 15. b6; 16. c7; 17. c6; 18. c5; 19. b6; 20. b5;
21. b4; 22. c5; 23. c4; 24. c3; 25. b4; 26. b3; 27. b2; 28. c3; 29. a2; 30. a1;
31. b2; 32. a2; 33. c3; 34. d5; 35. d4; 36. d3; 37. d2; 38. d1; 39. c3; 40. b2;
41. d1; 42. d2; 43. d3; 44. d4; 45. c3; 46. c2; 47. d2; 48. d1; 49. b2; 50. c2;
51. d2; 52. e2; 53. e3; 54. d1; 55. d2; 56. d3; 57. d4; 58. d5; 59. e3; 60. e4;
61. d3; 62. d4; 63. e4; 64. e5; 65. e6; 66. d6; 67. e7; 68. d5; 69. e5; 70. d4;
71. d5; 72. e5; 73. e6; 74. d5; 75. e5; 76. d6; 77. d7; 78. d8; 79. e8; 80. f8;
81. h7; 82. g8; 83. e7; 84. e6; 85. f8; 86. e7; 87. g8; 88. f8; 89. f7; 90. h8;
91. g8

• Note: I think Dr Xorile should get the green tick, I would not have got this without their answer! Commented Nov 29, 2016 at 7:00
• Well done! My best was only 108 moves. Commented Nov 29, 2016 at 7:24
• Very nice optimization. Commented Nov 29, 2016 at 14:01

I found the following 70 move solution:

e7 f8 e8 d8 e7 c8 c7 b8 b7 b6 c7 d8 e8 f8 h7 g8 e7 d7 f8 e8 d8 c7 c6 c5 d7 d6 d5 d4 d3 c5 b6 b5 b4 c5 c4 c3 b4 b3 b2 c3 a2 a1 b2 a2 c3 b2 d3 d4 c3 d3 e3 e4 e5 d4 d5 d6 e5 e6 d6 d7 e7 e8 f8 f7 e6 e7 g8 f7 h8 g8

My solution is inspired by Jonathan Allan's.

Could someone explain to me how I can make an animation like the other responders did?

• Very well done! I'd be interested in knowing how users are creating animations too. Maybe they are taking screenshots and using a GIF generator? Commented Nov 29, 2016 at 19:00
• This notation is illegible to me. How is e7 even a first possibile move? And the pieces aren't even stated anywhere in it! Commented Aug 21, 2019 at 17:37
• There is only one free square at any given move. Each move in the sequence indicates the piece that is moving to the free square. Commented Aug 22, 2019 at 18:58