266 lines
11 KiB
Plaintext
266 lines
11 KiB
Plaintext
{
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"cells": [
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{
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"cell_type": "markdown",
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"id": "google",
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"metadata": {},
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"source": [
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"##### Copyright 2025 Google LLC."
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]
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},
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{
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"cell_type": "markdown",
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"id": "apache",
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"metadata": {},
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"source": [
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"Licensed under the Apache License, Version 2.0 (the \"License\");\n",
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"you may not use this file except in compliance with the License.\n",
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"You may obtain a copy of the License at\n",
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"\n",
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" http://www.apache.org/licenses/LICENSE-2.0\n",
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"\n",
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"Unless required by applicable law or agreed to in writing, software\n",
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"distributed under the License is distributed on an \"AS IS\" BASIS,\n",
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"WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.\n",
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"See the License for the specific language governing permissions and\n",
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"limitations under the License.\n"
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]
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},
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{
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"cell_type": "markdown",
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"id": "basename",
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"metadata": {},
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"source": [
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"# nurses_cp"
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]
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},
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{
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"cell_type": "markdown",
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"id": "link",
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"metadata": {},
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"source": [
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"<table align=\"left\">\n",
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"<td>\n",
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"<a href=\"https://colab.research.google.com/github/google/or-tools/blob/main/examples/notebook/contrib/nurses_cp.ipynb\"><img src=\"https://raw.githubusercontent.com/google/or-tools/main/tools/colab_32px.png\"/>Run in Google Colab</a>\n",
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"</td>\n",
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"<td>\n",
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"<a href=\"https://github.com/google/or-tools/blob/main/examples/contrib/nurses_cp.py\"><img src=\"https://raw.githubusercontent.com/google/or-tools/main/tools/github_32px.png\"/>View source on GitHub</a>\n",
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"</td>\n",
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"</table>"
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]
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},
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{
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"cell_type": "markdown",
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"id": "doc",
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"metadata": {},
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"source": [
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"First, you must install [ortools](https://pypi.org/project/ortools/) package in this colab."
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]
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},
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{
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"cell_type": "code",
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"execution_count": null,
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"id": "install",
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"metadata": {},
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"outputs": [],
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"source": [
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"%pip install ortools"
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]
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},
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{
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"cell_type": "code",
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"execution_count": null,
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"id": "code",
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"metadata": {},
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"outputs": [],
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"source": [
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"import sys\n",
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"from ortools.constraint_solver import pywrapcp\n",
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"\n",
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"\n",
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"def main():\n",
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" # Creates the solver.\n",
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" solver = pywrapcp.Solver(\"schedule_shifts\")\n",
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"\n",
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" num_nurses = 4\n",
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" num_shifts = 4 # Nurse assigned to shift 0 means not working that day.\n",
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" num_days = 7\n",
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" # [START]\n",
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" # Create shift variables.\n",
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" shifts = {}\n",
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"\n",
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" for j in range(num_nurses):\n",
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" for i in range(num_days):\n",
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" shifts[(j, i)] = solver.IntVar(0, num_shifts - 1,\n",
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" \"shifts(%i,%i)\" % (j, i))\n",
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" shifts_flat = [\n",
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" shifts[(j, i)] for j in range(num_nurses) for i in range(num_days)\n",
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" ]\n",
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"\n",
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" # Create nurse variables.\n",
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" nurses = {}\n",
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"\n",
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" for j in range(num_shifts):\n",
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" for i in range(num_days):\n",
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" nurses[(j, i)] = solver.IntVar(0, num_nurses - 1,\n",
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" \"shift%d day%d\" % (j, i))\n",
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" # Set relationships between shifts and nurses.\n",
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" for day in range(num_days):\n",
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" nurses_for_day = [nurses[(j, day)] for j in range(num_shifts)]\n",
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"\n",
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" for j in range(num_nurses):\n",
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" s = shifts[(j, day)]\n",
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" solver.Add(s.IndexOf(nurses_for_day) == j)\n",
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" # Make assignments different on each day\n",
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" for i in range(num_days):\n",
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" solver.Add(solver.AllDifferent([shifts[(j, i)] for j in range(num_nurses)]))\n",
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" solver.Add(solver.AllDifferent([nurses[(j, i)] for j in range(num_shifts)]))\n",
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" # Each nurse works 5 or 6 days in a week.\n",
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" for j in range(num_nurses):\n",
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" solver.Add(solver.Sum([shifts[(j, i)] > 0 for i in range(num_days)]) >= 5)\n",
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" solver.Add(solver.Sum([shifts[(j, i)] > 0 for i in range(num_days)]) <= 6)\n",
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" # Create works_shift variables. works_shift[(i, j)] is True if nurse\n",
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" # i works shift j at least once during the week.\n",
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" works_shift = {}\n",
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"\n",
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" for i in range(num_nurses):\n",
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" for j in range(num_shifts):\n",
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" works_shift[(i, j)] = solver.BoolVar(\"nurse%d shift%d\" % (i, j))\n",
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"\n",
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" for i in range(num_nurses):\n",
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" for j in range(num_shifts):\n",
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" solver.Add(works_shift[(\n",
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" i, j)] == solver.Max([shifts[(i, k)] == j for k in range(num_days)]))\n",
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"\n",
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" # For each shift (other than 0), at most 2 nurses are assigned to that shift\n",
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" # during the week.\n",
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" for j in range(1, num_shifts):\n",
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" solver.Add(\n",
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" solver.Sum([works_shift[(i, j)] for i in range(num_nurses)]) <= 2)\n",
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" # If s nurses works shifts 2 or 3 on, he must also work that shift the previous\n",
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" # day or the following day.\n",
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" solver.Add(\n",
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" solver.Max(nurses[(2,\n",
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" 0)] == nurses[(2,\n",
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" 1)], nurses[(2,\n",
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" 1)] == nurses[(2,\n",
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" 2)]) == 1)\n",
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" solver.Add(\n",
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" solver.Max(nurses[(2,\n",
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" 1)] == nurses[(2,\n",
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" 2)], nurses[(2,\n",
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" 2)] == nurses[(2,\n",
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" 3)]) == 1)\n",
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" solver.Add(\n",
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" solver.Max(nurses[(2,\n",
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" 2)] == nurses[(2,\n",
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" 3)], nurses[(2,\n",
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" 3)] == nurses[(2,\n",
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" 4)]) == 1)\n",
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" solver.Add(\n",
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" solver.Max(nurses[(2,\n",
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" 3)] == nurses[(2,\n",
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" 4)], nurses[(2,\n",
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" 4)] == nurses[(2,\n",
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" 5)]) == 1)\n",
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" solver.Add(\n",
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" solver.Max(nurses[(2,\n",
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" 4)] == nurses[(2,\n",
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" 5)], nurses[(2,\n",
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" 5)] == nurses[(2,\n",
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" 6)]) == 1)\n",
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" solver.Add(\n",
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" solver.Max(nurses[(2,\n",
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" 5)] == nurses[(2,\n",
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" 6)], nurses[(2,\n",
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" 6)] == nurses[(2,\n",
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" 0)]) == 1)\n",
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" solver.Add(\n",
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" solver.Max(nurses[(2,\n",
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" 6)] == nurses[(2,\n",
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" 0)], nurses[(2,\n",
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" 0)] == nurses[(2,\n",
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" 1)]) == 1)\n",
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"\n",
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" solver.Add(\n",
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" solver.Max(nurses[(3,\n",
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" 0)] == nurses[(3,\n",
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" 1)], nurses[(3,\n",
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" 1)] == nurses[(3,\n",
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" 2)]) == 1)\n",
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" solver.Add(\n",
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" solver.Max(nurses[(3,\n",
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" 1)] == nurses[(3,\n",
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" 2)], nurses[(3,\n",
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" 2)] == nurses[(3,\n",
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" 3)]) == 1)\n",
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" solver.Add(\n",
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" solver.Max(nurses[(3,\n",
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" 2)] == nurses[(3,\n",
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" 3)], nurses[(3,\n",
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" 3)] == nurses[(3,\n",
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" 4)]) == 1)\n",
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" solver.Add(\n",
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" solver.Max(nurses[(3,\n",
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" 3)] == nurses[(3,\n",
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" 4)], nurses[(3,\n",
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" 4)] == nurses[(3,\n",
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" 5)]) == 1)\n",
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" solver.Add(\n",
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" solver.Max(nurses[(3,\n",
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" 4)] == nurses[(3,\n",
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" 5)], nurses[(3,\n",
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" 5)] == nurses[(3,\n",
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" 6)]) == 1)\n",
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" solver.Add(\n",
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" solver.Max(nurses[(3,\n",
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" 5)] == nurses[(3,\n",
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" 6)], nurses[(3,\n",
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" 6)] == nurses[(3,\n",
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" 0)]) == 1)\n",
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" solver.Add(\n",
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" solver.Max(nurses[(3,\n",
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" 6)] == nurses[(3,\n",
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" 0)], nurses[(3,\n",
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" 0)] == nurses[(3,\n",
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" 1)]) == 1)\n",
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" # Create the decision builder.\n",
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" db = solver.Phase(shifts_flat, solver.CHOOSE_FIRST_UNBOUND,\n",
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" solver.ASSIGN_MIN_VALUE)\n",
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" # Create the solution collector.\n",
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" solution = solver.Assignment()\n",
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" solution.Add(shifts_flat)\n",
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" collector = solver.AllSolutionCollector(solution)\n",
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"\n",
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" solver.Solve(db, [collector])\n",
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" print(\"Solutions found:\", collector.SolutionCount())\n",
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" print(\"Time:\", solver.WallTime(), \"ms\")\n",
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" print()\n",
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" # Display a few solutions picked at random.\n",
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" a_few_solutions = [859, 2034, 5091, 7003]\n",
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"\n",
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" for sol in a_few_solutions:\n",
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" print(\"Solution number\", sol, \"\\n\")\n",
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"\n",
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" for i in range(num_days):\n",
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" print(\"Day\", i)\n",
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" for j in range(num_nurses):\n",
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" print(\"Nurse\", j, \"assigned to task\",\n",
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" collector.Value(sol, shifts[(j, i)]))\n",
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" print()\n",
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"\n",
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"\n",
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"main()\n",
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"\n"
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]
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}
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],
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"metadata": {
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"language_info": {
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"name": "python"
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}
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},
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"nbformat": 4,
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"nbformat_minor": 5
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}
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