Draw Christmas names with Constraint Programming

Christmas names with constraint programming.ipynb

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     "text": [
      "Mam buys for Johanna\n",
      "Bart buys for Alice\n",
      "Dad buys for Belle\n",
      "Jonathan buys for Rhonda\n",
      "Robert buys for Alex\n",
      "Alex buys for Robert\n",
      "Rhonda buys for Jonathan\n",
      "Belle buys for Dad\n",
      "Alice buys for Bart\n",
      "Johanna buys for Mam\n"
     ]
    }
   ],
   "source": [
    "from ortools.sat.python import cp_model\n",
    "from random import shuffle\n",
    "\n",
    "persons = ['Mam', 'Dad', 'Bart', 'Belle', 'Jonathan', 'Johanna', 'Alex', 'Alice', 'Robert', 'Rhonda']\n",
    "shuffle(persons)\n",
    "forbidden = [\n",
    "    ['Mam', 'Dad'],\n",
    "    ['Bart', 'Belle',],\n",
    "    ['Jonathan', 'Johanna'],\n",
    "    ['Alex', 'Alice'],\n",
    "    ['Robert', 'Rhonda']\n",
    "]\n",
    "\n",
    "\n",
    "model = cp_model.CpModel()\n",
    "\n",
    "variables = {}\n",
    "\n",
    "for buyer in persons:\n",
    "    receiver_dict = {}\n",
    "    for receiver in persons:\n",
    "        receiver_dict[receiver] = model.NewIntVar(0, 1, f'{buyer} buys for {receiver}')\n",
    "    variables[buyer] = receiver_dict\n",
    "\n",
    "\n",
    "for name, buyer in variables.items():\n",
    "    model.Add(sum(buyer.values()) == 1)\n",
    "\n",
    "for name in persons:\n",
    "    model.Add(sum([receivers[name] for buyer_name, receivers in variables.items()]) == 1)\n",
    "\n",
    "for name in persons:\n",
    "    model.Add(variables[name][name] == 0)\n",
    "\n",
    "for name_1, name_2 in forbidden:\n",
    "    model.Add(variables[name_1][name_2] == 0)\n",
    "    model.Add(variables[name_2][name_1] == 0)\n",
    "\n",
    "\n",
    "solver = cp_model.CpSolver()\n",
    "result = solver.Solve(model)\n",
    "\n",
    "if result == cp_model.FEASIBLE:\n",
    "    for buyer, buyer_vars in variables.items():\n",
    "        for receiver, var in buyer_vars.items():\n",
    "            if solver.Value(var):\n",
    "                print(var)"
   ]
  }
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