作者：Josh Chang

　　The Solution of The Puzzle

　　One ring to rule them all,

　　One ring to find them,

　　One ring to bring them all,

　　And in the darkness bind them...

　　the emissaries' journey continues...

　　Right now we have 4 emissaries left behind, and there’s an ancient bridge ahead of them which is about to collapse. The bridge can afford only 2 people pass through at one time. It takes different time for each of the 4 emissaries to cross over the bridge: A takes 1 min, B takes 2 min, C takes 9 min, D takes 10 min. And there’s another problem, it’s completely dark out there, so they have to pass the bridge with a electric torch. But there’s only 1 electric torch, and 1 torch only takes 2 people at one time. What’s more,we have another condition,if 2 people pass through the bridge,their speed follows the slower one. For instance, if A pass through the bridge with D,it takes them 10 min to across. And now, the ancient bridge is gonna collapse in 17 min, so they only got 17 min to pass through. What should they arrange to across the bridge? Would you help them find out the solution?

　　{check the answer below}

　　Solution:

　　step 1: A pass through with B (2 min)

　　step 2: A goes back (3 min by now)

　　step 3: A gives torch to C

　　step 4: C pass through with D (13 min by now)

　　step 5: C gives torch to B

　　step 6: B goes back (15 min by now)

　　step 7: B pass through with A (altogether 17 min)

　　Now you’re the Lord of the rings!