As written, each loop iteration in the LIST-SEARCH' procedure requires two tests: one for x ≠ L.nil and one for x.key ≠ k. Show how to eliminate the test for x ≠ L.nil in each iteration.

要求：

As written, each loop iteration in the LIST-SEARCH' procedure requires two tests:
one for x ≠ L.nil and one for x.key ≠ k. Show how to eliminate the test for
x ≠ L.nil in each iteration.

解法：

關鍵就是在while循環開始之前將哨兵sentinel的key值設為k，這樣while循環無論鏈表中是否查詢成功都會終止

偽代碼

LIST-SEARCH'(L, k)

1 L.nil.key = k

2 x = L.nil.next

3 while x.key ≠ k

4 　　x = x.next

5 if x == L.nil

6 　　L.nil.key = NIL

7 return x