Data commit

Task/N-queens-problem/Zkl/n-queens-problem-1.zkl

@@ -0,0 +1,10 @@
+fcn isAttacked(q, x,y) // ( (r,c), x,y ) : is queen at r,c attacked by q@(x,y)?
+   { r,c:=q; (r==x or c==y or r+c==x+y or r-c==x-y) }
+fcn isSafe(r,c,qs) // queen safe at (r,c)?, qs=( (r,c),(r,c)..) solution so far
+   { ( not qs.filter1(isAttacked,r,c) ) }
+fcn queensN(N=8,row=1,queens=T){
+   qs:=[1..N].filter(isSafe.fpM("101",row,queens)) #isSafe(row,?,( (r,c),(r,c).. )
+       .apply(fcn(c,r,qs){ qs.append(T(r,c)) },row,queens);
+   if (row == N) return(qs);
+   return(qs.apply(self.fcn.fp(N,row+1)).flatten());
+}

Task/N-queens-problem/Zkl/n-queens-problem-2.zkl

@@ -0,0 +1,3 @@
+queens := queensN(4);
+println(queens.len()," solution(s):");
+queens.apply2(Console.println);