Nested List Comprehension and Binary Search
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Nested List Comprehension Binary Search Python Programming for Non-Programer Department of Computer Science, NCCU {{}}
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Transcript of Nested List Comprehension and Binary Search
Nested List ComprehensionBinary SearchPython Programming for Non-ProgramerDepartment of Computer Science, NCCU
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{{}}List Comprehension
Binary search
Outlines
Review list comprehension
Advance to nested list comprehension
The concept of binary search
Implementation of binary search
Q & A (about today or assignment 5)
{{}}List Comprehension
Binary search
Review List Comprehension[expression for name in list if filter]
>>> li = [1,2,3,4,5,6,7,8,9,10]>>> [x**2 for x in li if x%2==0]
[4, 16, 36, 64, 100]
{{}}List Comprehension
Binary search
Nested List ComprehensionWhat is nest? list in list, for in for
for x in list1: for y in list2: #doing sth
[[1], [1,3], [1,3,5], [1,3,5,7]]
{{}}List Comprehension
Binary search
Case 1: List in List
[[2*x - 1 for x in range(1,y+1)] for y in [1,2,3,4]]
[[1], [1,3], [1,3,5], [1,3,5,7]]
{{}}List Comprehension
Binary search
Nested List ComprehensionWhat is nest? list in list, for in for
for x in list1: for y in list2: #doing sth
[[1], [1,3], [1,3,5], [1,3,5,7]]
{{}}List Comprehension
Binary search
Case 2: For in Forfor x in list1: for y in list2: #doing sth
>>> list1=['a','b','c','d']>>> list2=['1','2','3','4']>>> [x+y for x in list1 for y in list2]['a1', 'a2', 'a3', 'a4', 'b1', 'b2', 'b3', 'b4', 'c1', 'c2', 'c3', 'c4', 'd1', 'd2', 'd3', 'd4']
{{}}List Comprehension
Binary search
Binary Search
More effective than Linear search
For sorted sequence only
{{}}List Comprehension
Binary search
Demo!
Show in TA session
Source code: http://pastie.org/1409772
{{}}List Comprehension
Binary search
It’s your turn
Follow the Pseudo-code to build your own program.
Ask TA when you encouted a problem.
Good luck for final exam!
{{}}List Comprehension
Binary search
Pseudo-Codefunction binarySearch(Sequence, Target): low <- the beginning index of Sequence high <- the ending index of Sequence WHILE low less than high: mid <- the middle index of Sequence IF the middle value of Seqeunce larger then Target: high <- the middle of Sequence ELSE IF the middle value of Sequence less than Target: low <- the middle of Sequence ELSE: RETURN mid ENDIF ENDWHILE RETURN False
The End
