| { | |
| "name": "langford_n9__v7", | |
| "problem_type": "langford", | |
| "params": { | |
| "n": 9 | |
| }, | |
| "prompt": "Construct a Langford sequence L(2,9): a sequence of length 18 containing exactly 2 copies of each integer from 1 to 9, such that the two occurrences of each value v are exactly v+1 positions apart (so copies of 1 are 1 position apart, copies of 2 are 2 positions apart, etc.). Example: L(2,3) has solution [2, 3, 1, 2, 1, 3].\n\nReturn seq as a list of 18 integers in 1..9, or state \"UNSATISFIABLE\" if no such sequence exists.", | |
| "satisfiable": false, | |
| "solution": null, | |
| "difficulty": { | |
| "solve_time_ms": 2919.6, | |
| "search_space": 6402373705728000, | |
| "num_variables": 18, | |
| "num_constraints": 176, | |
| "num_edges": -1, | |
| "backend": "pycsp", | |
| "solve_tier": "hard", | |
| "solve_pct_global": 96.05, | |
| "solve_pct_type": 93.75 | |
| }, | |
| "partial_assignment": null | |
| } | |