The head of a hard disk serves requests following the shortest seek time first (SSTF) policy. The head is initially positioned at truck number 180.
Which of the request sets will cause the head to change its direction after servicing every request assuming that the head does not change direction if there is a tie in SSTF and all the requests arrive before the servicing starts?
(A) 11, 139, 170, 178, 181, 184, 201, 265
(B) 10, 138, 170, 178, 181, 185, 201, 265
(C) 10, 139, 169, 178, 181, 184, 201, 265
(D) 10, 138, 170, 178, 181, 185, 200, 265
Answer: (B)
Explanation: A. 180->181->184
B. 180->181->178->185->170->201->138->265->10
So, B is true
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