{
  "name": "costas_array_n7__v8_h",
  "problem_type": "costas_array",
  "params": {
    "n": 7
  },
  "prompt": "Find a Costas array of order 7: place 7 marks on an 7x7 grid, one per row and one per column, such that all 7*(6)/2 displacement vectors (dr, dc) between pairs of marks (with dc > 0) are pairwise distinct.\n\nReturn x as a list of 7 integers in 0..6, where x[c] is the row of the mark in column c (permutation), or state \"UNSATISFIABLE\" if no such array exists.\n\nPartial assignment (fixed values that must be respected):\n- x[1]=1\nReturn a complete solution consistent with these fixed assignments.",
  "satisfiable": true,
  "solution": {
    "x": [
      0,
      1,
      6,
      4,
      3,
      5,
      2
    ]
  },
  "difficulty": {
    "solve_time_ms": 897.2,
    "search_space": 5040,
    "num_variables": 7,
    "num_constraints": 8,
    "num_edges": -1,
    "backend": "pycsp",
    "solve_tier": "medium",
    "solve_pct_global": 57.33,
    "solve_pct_type": 38.89
  },
  "partial_assignment": {
    "x": {
      "1": 1
    }
  }
}