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a9e7957 | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 | {
"name": "langford_n7__v11_nh",
"problem_type": "langford",
"params": {
"n": 7
},
"prompt": "Construct a Langford sequence L(2,7): a sequence of length 14 containing exactly 2 copies of each integer from 1 to 7, 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 14 integers in 1..7, or state \"UNSATISFIABLE\" if no such sequence exists.",
"satisfiable": true,
"solution": {
"seq": [
1,
7,
1,
2,
5,
6,
2,
3,
4,
7,
5,
3,
6,
4
]
},
"difficulty": {
"solve_time_ms": 1875.0,
"search_space": 87178291200,
"num_variables": 14,
"num_constraints": 110,
"num_edges": -1,
"backend": "pycsp",
"solve_tier": "hard",
"solve_pct_global": 90.79,
"solve_pct_type": 56.25
},
"partial_assignment": null
}
|