Python – K difference Consecutive elements

Given a list of integer elements, check for each element if its difference with successive element is K.

Input : test_list = [5, 6, 3, 2, 5, 3, 4], K = 1 
Output : [True, False, True, False, False, True] 
Explanation : 5, 6; 3, 2; and 3, 4 have 1 diff. between them. 

Input : test_list = [5, 6, 3, 2, 5, 3, 4], K = 2 
Output : [False, False, False, False, True, False] 
Explanation : Only 5, 3 has 2 diff between it.

Method #1 : Using list comprehension

This is one of the ways in which this task can be performed. In this, we check for each element with next one, if difference is K then we tag it True, else False.

Python3

# Python3 code to demonstrate working of
# K difference Consecutive elements
# Using list comprehension

# initializing list
test_list = [5, 6, 3, 2, 5, 3, 4]

# printing original list
print("The original list : " + str(test_list))

# initializing K
K = 3

# using list comprehension and abs() to compute result
res = [True if abs(test_list[idx] - test_list[idx + 1]) == K else False
       for idx in range(len(test_list) - 1)]

# printing result
print("The difference list result : " + str(res))

Output

The original list : [5, 6, 3, 2, 5, 3, 4]
The difference list result : [False, True, False, True, False, False]

Time Complexity: O(n*n), where n is the elements of list
Auxiliary Space: O(n), where n is the size of list

Method #2 : Using zip() + list comprehension

This is another way in which this task can be performed. In this the consecutive list is paired using zip() and computations run through list comprehension.

Python3

# Python3 code to demonstrate working of
# K difference Consecutive elements
# Using zip() + list comprehension

# initializing list
test_list = [5, 6, 3, 2, 5, 3, 4]

# printing original list
print("The original list : " + str(test_list))

# initializing K
K = 3

# using list comprehension and abs() to compute result
# zip() used to pair Consecutive elements list
res = [abs(a - b) == K for a, b in zip(test_list, test_list[1:])]

# printing result
print("The difference list result : " + str(res))

Output

The original list : [5, 6, 3, 2, 5, 3, 4]
The difference list result : [False, True, False, True, False, False]

Time Complexity: O(n*n) where n is the number of elements in the list “test_list”. 
Auxiliary Space: O(n) where n is the number of elements in the list “test_list”. 

Method 3: Using a for loop:

Step-by-step approach:

• Import the numpy module as np.
• Create a list named test_list and initialize it with values [5, 6, 3, 2, 5, 3, 4].
• Print the original list using the print() function.
• Initialize a variable K with value 3.
• Create an empty list named res to store the result.
• Use a for loop to iterate over the range from 0 to len(test_list)-1. The loop variable i takes values 0, 1, 2, 3, 4, 5 (because len(test_list) is 7).
• In each iteration of the loop, use the abs() function to compute the absolute difference between the i-th and (i+1)-th elements of the test_list. If this absolute difference equals K, then append True to the res list, else append False.
• Print the result list using the print() function.

Python3

# Python3 code to demonstrate working of
# K difference Consecutive elements
# Using for loop

# initializing list
test_list = [5, 6, 3, 2, 5, 3, 4]

# printing original list
print("The original list : " + str(test_list))

# initializing K
K = 3

# initializing empty list for result
res = []

# using for loop and abs() to compute result
for i in range(len(test_list)-1):
    if abs(test_list[i] - test_list[i+1]) == K:
        res.append(True)
    else:
        res.append(False)

# printing result
print("The difference list result : " + str(res))

Output

The original list : [5, 6, 3, 2, 5, 3, 4]
The difference list result : [False, True, False, True, False, False]

Time complexity: O(n)
Auxiliary space: O(n) as well, where n is the length of the input list.