day 2, part 2!

20/20_2.awk

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+BEGIN{ RS = ""; FS="" }
+
+NR==1{
+	for(i=1;i<=NF;i++){
+		en[i-1] = $i=="#" ? 1 : 0
+	}
+	RS = "\n"
+	next
+}
+
+{
+	for(i=-1;i<=NF+2;i++){
+		if(i>=1 && i<=NF)
+			inp[i,NR-1] = $i=="#" ? 1 : 0
+		else
+			inp[i,NR-1] = 0
+	}
+}
+
+function wintonum(px,py){
+	nbit = 8; num=0
+	for(j=py-1;j<=py+1;j++){
+		for(i=px-1;i<=px+1;i++){
+			b = inp[i,j]=="" ? 0 : inp[i,j]
+			num += lshift( b, nbit)
+			nbit--
+		}
+	}
+	return num
+}
+
+function wintonum2(px,py,pss){
+	nbit = 8; num=0
+	for(j=py-1;j<=py+1;j++){
+		for(i=px-1;i<=px+1;i++){
+			b = inp[i,j]=="" ? (pss%2==0? en[0] : 0 ) : inp[i,j]
+			num += lshift( b, nbit)
+			nbit--
+		}
+	}
+	return num
+}
+
+END{
+	xmin=-1; xmax=NF+2
+	ymin=-1; ymax=NR+1
+
+	for(pass=1;pass<=50;pass++){
+
+		count = 0
+		for(y=ymin-pass; y<=ymax+pass; y++){
+			for(x=xmin-pass; x<=xmax+pass; x++){
+				wn = (pass==1) ? wintonum(x,y) : wintonum2(x,y,pass)
+				newinp[x,y] = en[ wn ]
+				count += en[ wn ]
+#				printf "%c", newinp[x,y]==1? "#" : "."
+			}
+#			print ""
+		}
+		print "pass",pass,"count:",count
+
+		delete inp
+		# copy result
+		for(p in newinp) inp[p] = newinp[p]
+		delete newinp
+	}
+
+}