River Crossing Puzzle: Three Cannibals and Three Anthropologists

Three cannibals and three anthropologists have to cross a river. The boat they have is only big enough for two people. If at any point in time there are more cannibals on one side of the river than anthropologists, the cannibals will eat them. What plan can the anthropologists use for crossing the river so they don’t get eaten? (Remember! the boat can’t cross the river by itself, someone has to be in it to row it across)
Note that if a boat with a cannibal and an anthropologist travels to a shore with one cannibal on it, then no. of cannibals > no. of anthropologists, even if you say the anthropologist immediately takes the boat back.


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Solution to the River Crossing Puzzle:

To simply let us denote the entities involved as follows;

Anthropologist be A
Cannibal be C
The boat be B
Let us consider that everyone is on the west coast and let us denote it by W
The East coast is the part where everyone has to go and let us denote it by E

Step 1:
Let A and C cross with B So we have the following on each coast
W [A, A, C, C]
E [A, C, B]

Step 2:
A returns
W [A, A, A, C, C, B]
E [C]

Step 3:
Two C cross with B
W [A, A, A]
E [C, C, C, B]

Step 4: C returns
W [A, A, A, C, B]
E [C, C]

Step 5:
Two A cross with B
W [A, C]
E [A, A, C, C, B]

Step 6 :
A and C return
W [A, A, C, C, B]
E [A, C]

Step 7:
Two A crosses
W [C, C]
E [A, A, A, C, B]

Step 8:
C returns
W [C, C, C, B]
E [A, A, A]

Step 9:
Two C crosses
W [C]
E [A, A, A, C, C, B]

Step 10:
C returns
W [C, C, B]
E [A, A, A, C]

Step 11:
Two C crosses
W [Empty]
E [A, A, A, C, C, C, B]