ALGO(T,k)
ST=LAST=ST_A=LAST=NIL
CT=T
while(ct!=NIL || st !=NIL)do
	if(ct!=NIL)then
		a=NIL
		b=NIL
		if(ct->key<k)then
			a=ct
			sta=push(sta,a)
			st=push(st,ct)
			ct=ct->dx
		else if(ct->key>k)then
			st=push(st,ct)
			ct=ct->sx
		else
			st=push(st,ct)
			ct=ct->dx
	else
		ct=top(st)
		if(ct->key<k)then //se tale if fosse vero entrerei nella I chiamata ricorsiva
			b=val
		else if(ct->key>k)then
			a=val
			sta=push(sta,a)
			b=ct
		else
			if(last!=ct->sx && ct->sx!=NIL)then
				a=val
				sta=push(sta,a)
				ct=ct->sx
			else
				if(ct->sx=NIL)then
					a=val
					b=NIL
				else
					a=top(sta)
					pop(sta)
					b=val
		ret=BEST(a,b,k)
		+ uscita dall'algoritmo