# Python data structures and algorithms 14th Day "two-point search"

Source: Internet
Author: User

1. How to find two points

Find the fastest speed for a sorted list

2. Code implementation

(1) Recursive implementation

`defBinary_search (Alist, item):ifLen (alist) = =0:returnFalseElse: Midpoint= Len (alist)//2ifalist[midpoint]==Item:returnTrueElse:          ifitem<Alist[midpoint]:returnBinary_search (Alist[:midpoint],item)Else:            returnBinary_search (alist[midpoint+1:],item) testlist= [0, 1, 2, 8, 13, 17, 19, 32, 42,]Print(Binary_search (Testlist, 3))Print(Binary_search (Testlist, 13))`

(2) Non-recursive implementation

`defBinary_search (Alist, item): First=0 Last= Len (alist)-1 whilefirst<=Last:midpoint= (first + last)/2ifAlist[midpoint] = =Item:returnTrueelifItem <Alist[midpoint]: last= Midpoint-1Else: First= Midpoint+1returnfalsetestlist= [0, 1, 2, 8, 13, 17, 19, 32, 42,]Print(Binary_search (Testlist, 3))Print(Binary_search (Testlist, 13))`

3. Complexity of Time

Optimal time Complexity: O (1)

Worst time complexity: O (LOGN)

Because it's a dichotomy. How many times does the representation have to be checked, that is Logn

Python data structures and algorithms 14th Day "two-point search"

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