Plants vs Zombies!

Several plants and zombies (no more than 20 creatures in total) came to the party “Plants VS Zombies”, and it turned out that all the creatures are of different heights. When a plant speaks to a lower creature, it tells the truth, and speaking to a higher creature, it lies. Zombies, on the other hand, lie to lower creatures, and tell the truth to higher ones.

When starting the party, each participant approached each other and said either “I am higher than you” or “I am lower." The phrase “I am lower” was repeated 20 times. Saying goodbye, everyone had to approach each one again and say “I am higher and I am a plant." If some creature could not say this phrase, then it clapped its hands. There were 18 claps. Calculate how many creatures came to the party, and arrange them by height. Link