Python – Maximum difference across lists

Given two lists, the task is to write a Python program to find maximum difference among like index elements. 

Examples:

Input : test_list1 = [3, 4, 2, 1, 7], test_list2 = [6, 2, 1, 9, 1]
Output : 8
Explanation : 9 – 1 = 8 is maximum difference across lists in same index.

Input : test_list1 = [3, 4, 2, 1, 17], test_list2 = [6, 2, 1, 9, 1]
Output : 16
Explanation : 17 – 1 = 16 is maximum difference across lists in same index.

Method 1 : Using list comprehension + max()

In this, difference is computed using abs() and iteration is done using list comprehension. The max() is used for the task of getting maximum difference among computed sub result.

Python3

# Python3 code to demonstrate working of
# Maximum difference across lists
# Using list comprehension + max()

# initializing lists
test_list1 = [3, 4, 2, 1, 7]
test_list2 = [6, 2, 1, 9, 1]

# printing original lists
print("The original list 1 is : " + str(test_list1))
print("The original list 2 is : " + str(test_list2))

# using max() to get maximum of extracted difference
res = max(abs(test_list2[idx] - test_list1[idx])
          for idx in range(len(test_list1)))

# printing result
print("Maximum difference among lists : " + str(res))

Output

The original list 1 is : [3, 4, 2, 1, 7]
The original list 2 is : [6, 2, 1, 9, 1]
Maximum difference among lists : 8

Time Complexity: O(n)
Auxiliary Space: O(n)

Method 2 : Using zip() + max()

In this pairing of like index elements is done using zip(). Rest all the functionality is similar to above method.

Python3

# Python3 code to demonstrate working of
# Maximum difference across lists
# Using zip() + max()

# initializing lists
test_list1 = [3, 4, 2, 1, 7]
test_list2 = [6, 2, 1, 9, 1]

# printing original lists
print("The original list 1 is : " + str(test_list1))
print("The original list 2 is : " + str(test_list2))

# using max() to get maximum of extracted difference
# zip() used to bind elements
res = max(abs(ele1 - ele2) for ele1, ele2 in zip(test_list1, test_list2))

# printing result
print("Maximum difference among lists : " + str(res))

Output:

The original list 1 is : [3, 4, 2, 1, 7]
The original list 2 is : [6, 2, 1, 9, 1]
Maximum difference among lists : 8

Time Complexity: O(n) where n is the number of elements in the list “test_list”. The zip() + max() is used to perform the task and it takes O(n) time.
Auxiliary Space: O(n) additional space of size O(n) is required

Method #3: Using abs(), for loop

Approach:

1. First we need to check if both lists have the same length or not.
2.  If not, then return “Lists have different lengths”.
3. Then iterate through both lists at the same time using a for loop and calculate the absolute difference between each corresponding element of both lists.
4. Keep track of the maximum difference found so far using a variable.
5. Return the maximum difference found.

Python3

# fn to return the max difference at same position in lists
def max_diff_lists(list1, list2):
    if len(list1) != len(list2):
        return "Lists have different lengths"
    max_diff = 0
    for i in range(len(list1)):
        diff = abs(list1[i] - list2[i])
        if diff > max_diff:
            max_diff = diff
    return max_diff


# Example usage
test_list1 = [3, 4, 2, 1, 7]
test_list2 = [6, 2, 1, 9, 1]

# Printing Inputs
print("The original list 1: ", test_list1)
print("The original list 2: ", test_list2)

# Calling fn, printing result
print("Maximum difference among lists is: ", max_diff_lists(test_list1, test_list2))
# This code is developed by mohan balaji battu

Output

The original list 1:  [3, 4, 2, 1, 7]
The original list 2:  [6, 2, 1, 9, 1]
Maximum difference among lists is:  8

Time Complexity: O(n)
Auxiliary Space: O(1)