My cat was a stray... training him to use litter box was so easy. Now, no litter box and he will not pee or poo at all. He did that once, he held his pee and poo for more than 24 hours coz the vet didn't put a litter box for him.. poor thing.

Training a cat takes patience but I found that some cats will naturally use a litter box, like my cat hahahah....