von Koch and MiniZinc

include"globals.mzn";
 
%
% Definition of data
%
 
% Number of nodes in the graph
int: nodes;
setofint: Nodes = 1..nodes;
 
% Connections
int: connections;
setofint: Connections = 1..connections;
array[Connections,1..2] ofint: ConnectionEdges;
 
%
% Instance from http://yetanothermathprogrammingconsultant.blogspot.se/2017/09/von-koch-and-z3.html
% The following data could be located in a minizinc data file instead.
%
nodes = 7;
connections = 6;
ConnectionEdges =
         [|  1,  2,
          |  1,  4,
          |  1,  7,
          |  2,  3,
          |  2,  5,
          |  5,  6,
          |];
 
%
% Model proper
%
 
array[Nodes] ofvar1..nodes: NodeLabel;
array[Connections] ofvar1..connections: ConnectionLabel;
 
constraintalldifferent(NodeLabel) :: domain;
 
constraintalldifferent(ConnectionLabel) :: domain;
 
constraintforall(connection in Connections) (
    ConnectionLabel[connection] = abs(NodeLabel[ConnectionEdges[connection, 1]] - NodeLabel[ConnectionEdges[connection, 2]])
);

 
solvesatisfy;
 
output [
  "NodeLabels: "++ show(NodeLabel) ++
  "ConnectionLabels: "++ show(ConnectionLabel) ++
  "\n"
  ];