int: n; array [1..n] of var 1..n: q; % queen in column i is in row q[i] include "alldifferent.mzn"; constraint alldifferent(q); % distinct rows constraint alldifferent([ q[i] + i | i in 1..n]); % distinct diagonals constraint alldifferent([ q[i] - i | i in 1..n]); % upwards+downwards % search solve :: int_search(q, first_fail, indomain_min) satisfy; output [ if fix(q[j]) == i then "Q" else "." endif ++ if j == n then "\n" else "" endif | i,j in 1..n]