4 people wish to cross a bridge at night. A group of at most two people may cros

Question

4 people wish to cross a bridge at night. A group of at most two people may cross at any time, and each group must have a flashlight. Only one flashlight is available among the 4 people, so some sort of shuttle arrangement must be made in order to return the flashlight so that more people may cross. Each person has a different crossing speed; the speed of a group is determined by the speed of the slower member (or either if they are of the same speed.) Your job is to determine a strategy that gets all 4 people across the bridge in the minimum time. Provide the total number of seconds it takes to get everyone across, as well as the groups that cross, in order. (There may be multiple optimal solutions, in that case, any of them are fine.) The speed of a person is given in the number of seconds it would take him to cross. (If he is the slower member of the group.)

Speeds:

1: 1

2: 2

3: 5

4: 10

Explanation / Answer

Let the Person Name along with thier speed be

A(1) , B(2) , C(5) , D(10)


As there is only 1 flashlight ,


Strategy is as follows:-

So in 17 sec , 4 ppl will be across the bridge.

Minimum time is 17 sec

Thanks, let me know if there is any concern.

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