Missionaries and Cannibals


Three distressed missionaries wish to take three cannibals across a wide river.
They are restricted, however, by the following conditions:
(1) They have only one boat.
(2) Only 2 people can ride in the boat for each crossing.
(3) All missionaries but only one cannibal can row the boat.
(4) There must never be fewer missionaries than cannibals on
    one side, for the cannibals will feast on the missionaries.
    (Count any people in the boat when it is on a given side
    as members of the group on that side).
How do they all cross the river?




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Here is the answer:

Designate the Missionaries as M1, M2, and M3;
and the cannibals as C1, C2, and C3, where C1 is the cannibal who can row.
(1) C1 and C2 cross, C1 returns.
(2) C1 and C3 cross, C1 returns.
(3) M1 and M2 cross, M1 and C3 return.
(4) M1 and C1 cross, M1 and C2 return.
(5) M1 and M3 cross, C1 returns.
(6) C1 and C2 cross, C1 returns.
(7) C1 and C3 cross.

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