{
  "name": "costas_array_n8__v6_nh",
  "problem_type": "costas_array",
  "params": {
    "n": 8
  },
  "prompt": "Find a Costas array of order 8: place 8 marks on an 8x8 grid, one per row and one per column, such that all 8*(7)/2 displacement vectors (dr, dc) between pairs of marks (with dc > 0) are pairwise distinct.\n\nReturn x as a list of 8 integers in 0..7, where x[c] is the row of the mark in column c (permutation), or state \"UNSATISFIABLE\" if no such array exists.",
  "satisfiable": true,
  "solution": {
    "x": [
      4,
      7,
      3,
      2,
      0,
      5,
      6,
      1
    ]
  },
  "difficulty": {
    "solve_time_ms": 880.3,
    "search_space": 40320,
    "num_variables": 8,
    "num_constraints": 9,
    "num_edges": -1,
    "backend": "pycsp",
    "solve_tier": "medium",
    "solve_pct_global": 56.95,
    "solve_pct_type": 27.78
  },
  "partial_assignment": null
}