#can someone who is proficient in Python

1 messages · Page 1 of 1 (latest)

dire anvil
#

I understand it as: freq is a fixed-sized array of arrays, where the size is that of the length of nums

elder isle
#

so this technique is called list comprehension right instead of the array.
We're just creating len(nums) + 1 deepcopies of empty arrays insides of freq

#

since freq only has 1 layer

#

this is a 1 by (len(nums) + 1) array

#

so what do I mean by deepcopy

#

well

#

we can look at an example here

# 
n = 10
grid1 = [[]] * n
grid2 = [[] for _ in range(n)]
#

here I created 2 arrays

#

both dimensions are 1 by n

#

by what is really the difference?

#

what do you think might happen if I do

# 
grid1[0].append(1)
grid2[0].append(1)
# 
grid1 will become 
[[1], [1], [1], [1], [1], [1], [1], [1], [1], [1]]
and grid2 is
[[1], [], [], [], [], [], [], [], [], []]
#

by doing

#

grid1 = [[]] * n

#

we're creating n shallow copies

#

for which each arrays in grid1

#

shares the same address

#

meaning

#

if we modify one of the created arrays

#

then we're modifying all

#

while, in comparison we're creating a deepcopy in grid2, each individual array is its own identity

dire anvil
#

wow, that is crazy LOL. thank you. so many details.