Initial data commit

Task/N-queens-problem/Maple/n-queens-problem.maple

@@ -0,0 +1,34 @@
+queens:=proc(n)
+  local a,u,v,m,aux;
+  a:=[$1..n];
+  u:=[true$2*n-1];
+  v:=[true$2*n-1];
+  m:=[];
+  aux:=proc(i)
+    local j,k,p,q;
+    if i>n then
+      m:=[op(m),copy(a)];
+    else
+      for j from i to n do
+        k:=a[j];
+        p:=i-k+n;
+        q:=i+k-1;
+        if u[p] and v[q] then
+          u[p]:=false;
+          v[q]:=false;
+          a[j]:=a[i];
+          a[i]:=k;
+          aux(i+1);
+          u[p]:=true;
+          v[q]:=true;
+          a[i]:=a[j];
+          a[j]:=k;
+        fi;
+      od;
+    fi;
+  end;
+  aux(1);
+  m
+end:
+
+for a in queens(8) do printf("%a\n",a) od;