How to list all posts without a category in Jekyll?

Question

How does one list all the posts in a Jekyll blog that do not have a specified category?

How to list all in a given category is described here.

Answer 1

{% for post in site.posts %}
  {% if post.categories contains 'postcategory' %}
    <h1>Do nothing</h1>
  {% else %}
    <h2>{{ post.title }}</h2>
  {% endif %}
{% endfor %}