212 lines
6.4 KiB
Plaintext
212 lines
6.4 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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"# traffic_lights"
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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/traffic_lights.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/traffic_lights.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": "markdown",
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"id": "description",
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"metadata": {},
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"source": [
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"\n",
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"\n",
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" Traffic lights problem in Google CP Solver.\n",
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"\n",
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" CSPLib problem 16\n",
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" http://www.cs.st-andrews.ac.uk/~ianm/CSPLib/prob/prob016/index.html\n",
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" '''\n",
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" Specification:\n",
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" Consider a four way traffic junction with eight traffic lights. Four of the\n",
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" traffic\n",
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" lights are for the vehicles and can be represented by the variables V1 to V4\n",
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" with domains\n",
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" {r,ry,g,y} (for red, red-yellow, green and yellow). The other four traffic\n",
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" lights are\n",
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" for the pedestrians and can be represented by the variables P1 to P4 with\n",
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" domains {r,g}.\n",
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"\n",
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" The constraints on these variables can be modelled by quaternary constraints\n",
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" on\n",
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" (Vi, Pi, Vj, Pj ) for 1<=i<=4, j=(1+i)mod 4 which allow just the tuples\n",
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" {(r,r,g,g), (ry,r,y,r), (g,g,r,r), (y,r,ry,r)}.\n",
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"\n",
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" It would be interesting to consider other types of junction (e.g. five roads\n",
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" intersecting) as well as modelling the evolution over time of the traffic\n",
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" light sequence.\n",
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" ...\n",
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"\n",
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" Results\n",
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" Only 2^2 out of the 2^12 possible assignments are solutions.\n",
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"\n",
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" (V1,P1,V2,P2,V3,P3,V4,P4) =\n",
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" {(r,r,g,g,r,r,g,g), (ry,r,y,r,ry,r,y,r), (g,g,r,r,g,g,r,r),\n",
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" (y,r,ry,r,y,r,ry,r)}\n",
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" [(1,1,3,3,1,1,3,3), ( 2,1,4,1, 2,1,4,1), (3,3,1,1,3,3,1,1), (4,1, 2,1,4,1,\n",
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" 2,1)}\n",
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"\n",
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" The problem has relative few constraints, but each is very tight. Local\n",
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" propagation\n",
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" appears to be rather ineffective on this problem.\n",
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"\n",
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" '''\n",
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"\n",
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" Note: In this model we use only the constraint solver.AllowedAssignments().\n",
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"\n",
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"\n",
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" Compare with these models:\n",
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" * MiniZinc: http://www.hakank.org/minizinc/traffic_lights.mzn\n",
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" * Comet : http://www.hakank.org/comet/traffic_lights.co\n",
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" * ECLiPSe : http://www.hakank.org/eclipse/traffic_lights.ecl\n",
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" * Gecode : http://hakank.org/gecode/traffic_lights.cpp\n",
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" * SICStus : http://hakank.org/sicstus/traffic_lights.pl\n",
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"\n",
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"\n",
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" This model was created by Hakan Kjellerstrand (hakank@gmail.com)\n",
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" Also see my other Google CP Solver models:\n",
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" http://www.hakank.org/google_or_tools/\n",
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"\n"
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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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"\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(base=10, start=1, len1=1, len2=4):\n",
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"\n",
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" # Create the solver.\n",
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" solver = pywrapcp.Solver(\"Traffic lights\")\n",
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"\n",
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" #\n",
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" # data\n",
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" #\n",
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" n = 4\n",
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" r, ry, g, y = list(range(n))\n",
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" lights = [\"r\", \"ry\", \"g\", \"y\"]\n",
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"\n",
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" # The allowed combinations\n",
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" allowed = []\n",
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" allowed.extend([(r, r, g, g), (ry, r, y, r), (g, g, r, r), (y, r, ry, r)])\n",
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"\n",
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" #\n",
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" # declare variables\n",
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" #\n",
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" V = [solver.IntVar(0, n - 1, \"V[%i]\" % i) for i in range(n)]\n",
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" P = [solver.IntVar(0, n - 1, \"P[%i]\" % i) for i in range(n)]\n",
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"\n",
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" #\n",
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" # constraints\n",
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" #\n",
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" for i in range(n):\n",
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" for j in range(n):\n",
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" if j == (1 + i) % n:\n",
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" solver.Add(solver.AllowedAssignments((V[i], P[i], V[j], P[j]), allowed))\n",
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"\n",
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" #\n",
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" # Search and result\n",
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" #\n",
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" db = solver.Phase(V + P, solver.INT_VAR_SIMPLE, solver.INT_VALUE_DEFAULT)\n",
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"\n",
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" solver.NewSearch(db)\n",
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" num_solutions = 0\n",
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" while solver.NextSolution():\n",
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" for i in range(n):\n",
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" print(\"%+2s %+2s\" % (lights[V[i].Value()], lights[P[i].Value()]), end=\" \")\n",
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" print()\n",
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" num_solutions += 1\n",
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"\n",
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" solver.EndSearch()\n",
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"\n",
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" print()\n",
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" print(\"num_solutions:\", num_solutions)\n",
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" print(\"failures:\", solver.Failures())\n",
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" print(\"branches:\", solver.Branches())\n",
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" print(\"WallTime:\", solver.WallTime())\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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