%
% colOpt: comput chromatic number (minimum number of colours required)
%

int: n;
array[1..n,1..n] of 0..1: A; % adjacency

% declare constrained integer variables
array[1..n] of var 1..n: v; % v[i] = j <-> ith vertex is given jth colour

% post constraints
constraint forall(i,j in 1..n where i<j)(if A[i,j] = 1 then v[i] != v[j] else true endif);

var 1..n: chi; % the chromatic number
constraint chi = max(v);

solve minimize chi;