A river crossing
On the left side of a river, there are 3 missionaries and 3 cannibals. The goal is to get all 6 people to the other side under the following constraints: They have a row-boat at their disposal that holds a maximum of 2 occupants. At no time, can there be more cannibals than missionaries, or lunch will be served. Defining a crossing as one way traverse across the river, how many crossings will be required for a safe journey, all 6 people arriving on the right side of the river?
The answer is 11.
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1 solution
Starting with MMMCCC on the left side, no one on the right, After the first crossing, we have MMMC on the left, CC on the right. Ahter the 2nd crossing, we have MMMCC on the left, C on the right. After the 3rd crossing, we have MMM on the left, CCC on the right. After the 4th crossing, we ave MMMC on the left, CC on the right. After the 5th crossing, we have MC on the left, MMCC on the right. After the 6th crossing, we have MMCC on the left, MC on the right. After the 7th crossing, we have CC on the left, MMMC on the right. After the 8th crossing, we have CCC on the left, MMM on the right. After the 9th crossing, we have C on the left, MMMCC on the right. After the 10th crossing, we have CC on the left, and MMMC on the right. After the 11th crossing, we have no one on the left, MMMCCC on the right, and everybody is hungry.