//STACK: T, x, ret

ALGO(T,k){
	st,sx,sret=NIL;
	lt=NIL;
	ct=T;
	WHILE (ct!=NIL || lt!= NIL) DO
		IF (ct!=NIL) THEN
			ret=infinito;
			x=ct->k%2;
			st=PUSH(st,ct);
			sx=PUSH(sx,x);
			ct=ct->sx;
		ELSE
			ct=TOP(st);
			x=TOP(sx);
			IF (lt!=ct->dx && ct->dx!=NIL) THEN
				y=elem;
				IF (x=k%2) THEN
					ret=0;
				ELSE
					ret=y;
				sret=PUSH(sret,ret);
				ct=ct->dx;
			ELSE
				IF (ct->dx!=NIL) THEN
					z=elem;
					ret=top(sret);
				ELSE
					y=elem
					IF (x=k%2) THEN
						ret=0;
					ELSE
						ret=y;
					z=infinito;
				ret=MIN(ret,z)+1;
				elem=ret;
				st=POP(st);
				sx=POP(sx);
				sret=POP(sret);
				lt=ct;
				ct=NIL;
	return elem;
}

DUBBI: serve lo stack per RET? e come gestirlo?