River Thames needs to be crossed by Mr. Father, Mrs. Mother, A Thug, A Policeman, 2 dogs and 2 Cats. There is only one boat, which can carry only two people (or a person and an animal or two animals) at a time. Only the humans (excluding the thug) know how to operate the boat. The boat must travel back and forth across the river in order to pick up all of the people and animals.
Following rules must be followed at all times:
Mr. Father: Mr. Father cannot stay with any of the cats, without Mrs. Mother's presence.
Mrs. Mother: Mrs. Mother cannot stay with any of the dogs, without Mr. Father's presence.
Thug: The thug cannot stay with anyone, if the policeman is not there.
Policeman Allowed to travel with everyone.
2 Dogs, 2 Cats: Not allowed to travel without a human, or be in the presence of the thug without the policeman's supervision.
The dogs are not allowed to be in the presence of Mrs. Mother without the supervision of Mr. Father.
Similarly, The cats are not allowed to be in the presence of Mr. Father without the supervision of Mrs. Mother.
Both the dogs and cats are allowed to be unsupervised (provided the other rules are satisfied.)
How will everyone get to the other side of the river Thames? None of the rule can be broken, and all rules apply on the boat as well as on the land.