Thursday, July 17, 2008

Crossing the bridge by four people

Four people need to cross the bridge in the night time with a single flashlight. The bridge can accommodate two people at a time.
The speed of all the people is different.
A can cross in 1 min
B can cross in 2 min
C can cross in 5 min
D can cross in 10 min
What is the minimum time to cross the bridge?

A & B cross (2min)
B comes back (2min)
C & D cross (10min)
A comes back (1min)
A & B cross (2min)
Total time=2+2+10+1+2=17min

Let me know if you have better solution.

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