Python | Increase list size by padding each element by N
Last Updated :
17 Apr, 2023
Given a list and an integer N, write a Python program to increase the size of the list by padding each element by N.
Examples:
Input : lst = [1, 2, 3]
N = 3
Output : [1, 1, 1, 2, 2, 2, 3, 3, 3]
Input : lst = ['cats', 'dogs']
N = 2
Output : ['cats', 'cats', 'dogs', 'dogs']
Approach #1 : List comprehension
Python3
# Python3 program to increase list size
# by padding each element by N
def increaseSize(lst, N):
return [el for el in lst for _ in range(N)]
# Driver code
lst = [1, 2, 3]
N = 3
print(increaseSize(lst, N))
Output:[1, 1, 1, 2, 2, 2, 3, 3, 3]
Time Complexity: O(n), where n is the number of elements in the list
Auxiliary Space: O(1), constant space needed
Approach #2 : Using functools.reduce() method The reduce function apply a particular function passed in its argument to all of the list elements. Therefore, in this approach we apply a function on each element where it's occurrence gets multiplied by N.
Python3
# Python3 program to increase list size
# by padding each element by N
from functools import reduce
def increaseSize(lst, N):
return reduce(lambda x, y: x + y, [[el]*N for el in lst])
# Driver code
lst = [1, 2, 3]
N = 3
print(increaseSize(lst, N))
Output:[1, 1, 1, 2, 2, 2, 3, 3, 3]
Approach #3 : Using itertools.chain()
Python3
# Python3 program to increase list size
# by padding each element by N
from itertools import chain
def increaseSize(lst, N):
return list(chain(*([el]*N for el in lst)))
# Driver code
lst = [1, 2, 3]
N = 3
print(increaseSize(lst, N))
Output:[1, 1, 1, 2, 2, 2, 3, 3, 3]
Approach #4 : Using * and extend() method
- Initiate a for loop to access list elements
- Repeat each list element by using * operator
- And add repeated elements to output list(using extend())
- Display output list
Python3
# Python3 program to increase list size
# by padding each element by N
lst = [1, 2, 3]
N = 3
x=[]
for i in lst:
x.extend([i]*N)
print(x)
Output[1, 1, 1, 2, 2, 2, 3, 3, 3]
Time Complexity : O(N)
Auxiliary Space : O(N)
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