day 18, part 2!

18/18_2.awk

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+function parse( s ){
+	delete sl; delete sr
+	while(length(s)>0){
+		if(match(s,/^[0-9]+/)){
+			num[++pindex] = substr(s,RSTART,RLENGTH)
+			s = substr(s,RSTART+RLENGTH)
+			continue
+		}
+		else if(s~/^\]/){ # ]
+			l = sl[slp--]
+			r = pindex
+#			print "left",l,"right",r
+			num[++pindex] = -1
+			ile[pindex] = l
+			iri[pindex] = r
+			if(slp==0) root = pindex
+		}
+		else if(s~/^,/){ # ,
+			sl[++slp] = pindex
+		}
+		s = substr(s,2)
+	}
+}
+
+function cleanparse(s){
+	delete ile; delete iri; delete num; delete sl
+	slp = 0
+	pindex = 0
+	parse(s)
+}
+
+function parent(id){
+	for(i in ile)
+		if(ile[i]==id || iri[i]==id) return i
+	return -1
+}
+
+function levels(id){
+	i = id
+	count = 0
+	if(id==root) return 0
+	do{
+		i = parent(i)
+		if(i<0) return -1
+		count++
+	}while(i!=root)
+	return count
+}
+
+function treetostring(id){
+	if(num[id]<0)
+		return "[" treetostring(ile[id]) "," treetostring(iri[id]) "]"
+	else
+		return num[id]
+}
+
+function leftitemi(id){
+	do{
+		id--
+	}while((num[id]<0 && id>0))
+	return id
+}
+
+function rightitemi(id){
+	do{
+		id++
+	}while((num[id]<0 && id<=length(num)))
+	return id
+}
+
+
+function explode(id){
+	lefti = leftitemi(id)
+	if(lefti>0){
+		num[lefti] += num[id]
+		num[id]=-1
+	}
+	righti = rightitemi(id)
+	rightrighti = rightitemi(righti)
+	if(rightrighti<=length(num)){
+		num[rightrighti] += num[righti]
+		num[righti] = -1
+	}
+	p = parent(id)
+	num[p] = 0
+}
+
+function toexplode(){
+	for(id=1;id<=pindex;id++){
+		if((num[id]>=0) && (levels(id)>4) && num[parent(id)]<0) return id
+	}
+	return -1
+}
+
+function dosplit(id){
+	n = num[id]
+	nl = int(n/2)
+	nr = int(n/2) + n%2
+	num[id] = -1
+	num[++pindex] = nl
+	ile[id] = pindex
+	num[++pindex] = nr
+	iri[id] = pindex
+}
+function tosplit(){
+	for(id=1;id<=pindex;id++){
+#		print id, (num[id]-10>0), num[id]
+		if((num[id]-10>=0) && num[parent(id)]<0 ) return id
+	}
+	return -1
+}
+
+function reduce(){
+	do{
+		ind = toexplode()
+		print "explode?", ind, num[ind], parent(ind), num[parent(ind)],num[leftitemi(ind)]
+
+		if(ind>0){
+			explode(ind)
+			print "exploded", treetostring(root)
+			s = treetostring(root)
+			cleanparse(s)
+#			print "to split?",tosplit()
+			continue
+		}
+		ind = tosplit()
+		print "split?", ind, num[ind], parent(ind), num[parent(ind)], ile[parent(ind)], iri[parent(ind)]
+		if(ind>0){
+			dosplit(ind)
+			print "split", treetostring(root)
+			s = treetostring(root)
+			cleanparse(s)
+		}
+		print toexplode(), tosplit()
+	} while( ((toexplode()>0) || (tosplit()>0)) )
+	print "done"
+}
+
+function magnitude(id){
+	if(num[id]>=0) return num[id] # regular number
+	# node
+	return magnitude(ile[id])*3 + magnitude(iri[id])*2
+}
+
+BEGIN{ pindex = 0 }
+
+{ line[NR] = $0 }
+
+END{
+	print NR
+	maxmag = 0
+	for(a=1;a<=NR;a++){
+		for(b=1;b<=NR;b++){
+			if(a!=b){
+				print "parsing", a, b
+				cleanparse( line[a] )
+				proot = root
+				parse( line[b] )
+				num[++pindex] = -1
+				ile[pindex] = proot
+				iri[pindex] = root
+				root = pindex
+				reduce()
+				if(magnitude(root)>maxmag){
+					maxmag=magnitude(root)
+					maxs = treetostring(root)
+					maxa = a
+					maxb = b
+				}
+			}
+		}
+	}
+	print maxmag, maxs, maxa, maxb
+}