Python – Replacing by Greatest Neighbour in list
Given a list, the task is to write a Python program to replace with the greatest neighbor among previous and next elements.
Input : test_list = [5, 4, 2, 5, 8, 2, 1, 9],
Output : [5, 5, 5, 8, 8, 8, 9, 9]
Explanation : 4 is having 5 and 2 as neighbours, replaced by 5 as greater than 2.Input : test_list = [5, 4, 2, 5],
Output : [5, 5, 5, 5]
Explanation : 4 is having 5 and 2 as neighbours, replaced by 5 as greater than 2.
Method 1 : Using loop + chain conditional statements
In this, we use loop to iterate through all the elements in list and check for neighbours for greater element using conditionals and then is replaced.
Python3
# Python3 code to demonstrate working of# Replacing by Greatest Neighbour# Using loop + chain conditional statements# initializing listtest_list = [5, 4, 2, 5, 8, 2, 1, 9]# printing original listprint("The original list is : " + str(test_list))for idx in range(1, len(test_list) - 1): # replacing by greater Neighbour test_list[idx] = test_list[idx - 1] \ if test_list[idx - 1] > test_list[idx + 1] \ else test_list[idx + 1]# printing resultprint("The elements after replacing : " + str(test_list)) |
Output:
The original list is : [5, 4, 2, 5, 8, 2, 1, 9] The elements after replacing : [5, 5, 5, 8, 8, 8, 9, 9]
Time Complexity: O(n)
Auxiliary Space: O(1)
Method 2 : Using max() + loop.
In this, we get the maximum element among neighbouring elements using max(). The loop is used to iterate through the elements.
Python3
# Python3 code to demonstrate working of # Replacing by Greatest Neighbour# Using max() + loop# initializing listtest_list = [5, 4, 2, 5, 8, 2, 1, 9]# printing original listprint("The original list is : " + str(test_list))for idx in range(1, len(test_list) - 1): # using max() to get maximum of Neighbours test_list[idx] = max(test_list[idx - 1], test_list[idx + 1]) # printing result print("The elements after replacing : " + str(test_list)) |
Output:
The original list is : [5, 4, 2, 5, 8, 2, 1, 9] The elements after replacing : [5, 5, 5, 8, 8, 8, 9, 9]
Time Complexity: O(n*n)
Auxiliary Space: O(n)
