Problem statement: Four people need to cross a weak bridge at night. They have only one flashlight and battery only can last for 17 hours; Bridge can only support 2 people at a time Now the diversity is different people can cross it in different speeds. Some fast and some slow. p can cross in 1 minute q can cross in 2 minute r can cross in 5 minute s can cross in 10 minute When two are walking together, they walk together :) can u do it in 17 minutes?

P,Q GO 2 minutes. Q comes back with light 2+2 =4 R,S GO 2 minutes. P comes back with light 10+1 =11 P,Q Go ==2 Idea is -- faster people have to do double shuttle. And group the slowest to go together.