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Python – Alternate elements Similarity

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  • Last Updated : 01 Aug, 2020
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Given list of elements, check if all the alternate elements are equal to K.

Input : test_list = [5, 3, 5, 2, 5, 8, 9], K = 5
Output : False
Explanation : 9 != 5, hence False.

Input : test_list = [4, 3, 4, 2, 4], K = 4
Output : True
Explanation : All alternates equal to 4.

Method #1 : Using loop

This is brute way to solution to this problem. In this, iterate for each element in list and check for each element if they are equal to K.

Python3




# Python3 code to demonstrate working of 
# Alternate elements Similarity
# Using loop
  
# initializing lists
test_list = [5, 3, 5, 2, 5, 8, 5]
  
# printing original list
print("The original list : " + str(test_list))
  
# initializing K 
K = 5
  
# using flag to Flag false if any one element is not K 
# using loop to check for each element
res = True
for idx, ele in enumerate(test_list):
    if not idx % 2 and ele != K: 
        res = False 
        break
  
# printing result 
print("Are all alternate elements equal to K : " + str(res))

Output

The original list : [5, 3, 5, 2, 5, 8, 5]
Are all alternate elements equal to K : True

Method #2 : Using all() + generator expression

This is yet another way in which this task can be performed. In this, we check for all elements using all() and generator expression is used for condition check and iteration.

Python3




# Python3 code to demonstrate working of 
# Alternate elements Similarity
# Using all() + generator expression
  
# initializing lists
test_list = [5, 3, 5, 2, 5, 8, 5]
  
# printing original list
print("The original list : " + str(test_list))
  
# initializing K 
K = 5
  
# all() to encapsulate whole logic into one expression
res = all(test_list[idx] == K for idx in range(0, len(test_list), 2))
  
# printing result 
print("Are all alternate elements equal to K : " + str(res))

Output

The original list : [5, 3, 5, 2, 5, 8, 5]
Are all alternate elements equal to K : True

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