[英]A query regarding the algorithm of binary search using C
In Binary Search Algorithm
, 在
Binary Search Algorithm
,
in general 一般来说
if mid_value > search_element we set high = mid_pos-1 ;
else mid_value < search_element we set low = mid_pos+1 ;
But I've just modified the algorithm like these 但是我已经像这样修改了算法
if mid_value > search_element we set high = mid_pos ;
else mid_value < search_element we set low = mid_pos ;
But my teacher told me that the standard algorithm for binary search
is the first one and what you have written is also a search algorithm but it's not an algorithm for binary search. 但是我的老师告诉我,
binary search
的标准算法是第一个算法,您写的也是搜索算法,但它不是二进制搜索的算法。 Is he correct?. 他说的对吗?
Your Algo is not correct : 您的算法不正确:
case : list [1, 2] , searchElem = 2 , low = 0,high = 1 case:list [1,2],searchElem = 2,low = 0,high = 1
mid = (low+high)/2 = (0+1)/2 = 0 中=(低+高)/ 2 =(0 + 1)/ 2 = 0
mid < searchElem set low = mid updated mid = 0, high = 1 [list didn't change] mid <searchElem设置低=更新中= 0,高= 1 [列表没有变化]
so you will end up with infinite loop. 因此您将陷入无限循环。
I think you picked it up wrongly . 我想你把它弄错了。
The basic Binary Search Algorithm
's workflow: 基本的
Binary Search Algorithm
的工作流程:
Procedure binary_search
A ← sorted array
n ← size of array
x ← value to be searched
Set lowerBound = 1
Set upperBound = n
while x not found
if upperBound < lowerBound
EXIT: x does not exists.
set midPoint = lowerBound + ( upperBound - lowerBound ) / 2
if A[midPoint] < x
set lowerBound = midPoint + 1
if A[midPoint] > x
set upperBound = midPoint - 1
if A[midPoint] = x
EXIT: x found at location midPoint
end while
end procedure
Here you can see what actually midPoint = lowerBound + ( upperBound - lowerBound ) / 2
, lowerBound = midPoint + 1
and upperBound = midPoint - 1
does . 在这里,您可以看到
midPoint = lowerBound + ( upperBound - lowerBound ) / 2
, lowerBound = midPoint + 1
和upperBound = midPoint - 1
作用。
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