You guessed it, diodes can also be used to build logic gates, but not all of them, only the AND and OR gates can be built using diodes only. However, by adding a transistor as an active element ...

NAND and NOR gates, and Minecraft redstone. Conventional wisdom says you can’t build a flip-flop with just one transistor, but here we are. [roelh] has built a flip-flop circuit using only one ...

7. A crude voltage multiplier. Use #2: Diode Logic Gates You can build simple logic gates using diodes. You can create an n-input OR gate or AND gate using 1 diode per input (Fig. 8). 8.