Saw this code on leetcode and don't get what it does or how it works. Paths is a list of lists.
def solution(paths):
s = set(p[0] for p in paths)
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it's a function that take an 2-D array(arrays inside an array), then second line loop through 2-D array and take first element of the Nested array and store it in a set which is like an unordered list where elements can't be repeated then return final setKMG– KMG2020-10-10 02:02:16 +00:00Commented Oct 10, 2020 at 2:02
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2 Answers
Ok not sure which part of the code you were referring to.
def solution(**paths**): #1
s = set(p[0] for p in paths) #2
#1 creates a function called solution, that takes one argument (path)
#2 assigns a set to the variable s.
set( ) is a function creates a set object.
p[0] is the item you want from the forloop. and you are grabbing the first variable in each set that is in path
it can also be interpeted as:
def solution(paths):
s = {} # declare variable
for item in path: # use forloop
s.add(item[0]) #add the first element of each item in path (the set in path)
print(s)
test_path = [ ['a','b','c'] , ['a','e','f'], ['g','h','i'] ]
solution(test_path)
notice in the results printed below that only one of the 'a' is added because a set only has unique variables
>>>{'g', 'a'}
You can do some Research on list comprehensions. I only started learning Python a few months ago myself. but i found this great video that I think explains the different types of comprehensions very well.
Comments
p is a list, and p[0] takes the first item in the sub-list, and this gets added to a set (i.e., duplicates are removed).
For example, if paths = [[1,2,3] , [1,3,4], [2,3,4]]
s = {1, 2}
Note that function doesn't return anything since it does not have 'return'.
