Do I have to cite common CS algorithms?
Do I have to cite common CS algorithms?


No. 

The fact that it was first published [in] 1961 isn't relevant, you needn't cite it because it is [widely] used and [well-]known by almost anyone in the CS world. 

That said, although a citation isn't necessary, you can provide one at your discretion. Such a citation is probably more important for a final thesis than for an academic publication, since it may be considered important for students to demonstrate they can cite. 

Beyond citing the original source, you may like to cite your favourite textbook(s) on the topic (rather than citing the entire volume, reference a particular section, e.g., \cite[Chapter 4.3]{Textbook} in LaTeX).