[理工] [OS]-成大98-資工

[lovefo (lovefo)]

Suppose that a disk drive has 5000 cylinders,numbered 0 to 4999.The drive is
currently
serving a request at cylinder 143,and the previous requeest was at cylinder
100.The queue of
pending requests,in FIFO order is
                         86,1470,913,1774,948,1509,1022,1750,130
Starting from the current head position,what is the total distance (in
cylinders) that the
disk arm moves to satisfy all the pending requests if the C-LOOK
disk-scheduling algorithm is used?



143  ->  913  -> 948  ->  1022  ->  1470  ->  1509  ->  1750  ->  1774  ->  86
     770      35      74        448       39        241       24        1688

->  130
44

770+35+74+448+39+241+24+1688+44=3363


我算出來 答案是3363
和某位大大算出來有極大的差異
不知道我是哪裡錯了
希望其他大大能給我指教

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推 lightergogo:沒錯阿
推 polomoss:沒錯~
→ polomoss:還有你不需要每個加~~用尾巴去減比較快
推 newman1125:我算的是 (4999-143) + (130-0) = 4986 不是ㄇ?
推 yesa315:原PO正確 相信自己一點!
推 daven329:(1774-143)+(1774-86)+(130-86)=3363
→ polomoss:樓上正解，這樣比較快