Python Program to Sort a List in Wave Form

In the previous article, we have discussed Python Program for Alternative Sorting.
Waveform:

Sort an unsorted list of integers into a wave-like list given an unsorted list of integers.

If list[0..n-1] >= list[1] <= list[2] >= list[3] <= list[4] >=….., a  ‘list[0..n-1]’ is sorted in wave form.

Examples:

Example1:

Input:

Given List = [1, 5, 7, 2, 4, 6, 9]

Output:

The above given list after sorted in waveform :
2 1 5 4 7 6 9

Example2:

Input:

Given List = [12, 34, 10, 8, 90, 75, 89]

Output:

The above given list after sorted in waveform :
10 8 34 12 89 75 90

Program to Sort a List in Wave Form in Python

Below are the ways to sort a given list in the form of the waveform:

Method #1: Using For Loop (Static Input)

Approach:

• Give the list as static input and store it in a variable.
• Sort the above-given list using the sort() function.
• Calculate the length of the given list using the len() function and store it in another variable.
• Loop from 0 to length of the given list with a step size of 2 using the for loop.
• Inside the loop, assign a given list of (iterator +1) values to the given list of iterator and a given list of the iterator to the given list of iterator+1.
• Loop from 0 to length of the given list using the for loop.
• Inside the loop, print the given list of iterator values to sort the list in a waveform.
• The Exit of the Program.

Below is the implementation:

# Give the list as static input and store it in a variable.
gvn_lst = [1, 5, 7, 2, 4, 6, 9]
# Sort the above-given list using the sort() function.
gvn_lst.sort()
# Calculate the length of the given list using the len() function and
# store it in another variable.
len_lst = len(gvn_lst)
# Loop from 0 to length of the given list with a step size of 2 using the for loop.
for itr in range(0, len_lst-1, 2):
# Assign a given list of (iterator +1) values to the given list of iterator and
# a given list of the iterator to the given list of iterator+1.
gvn_lst[itr], gvn_lst[itr+1] = gvn_lst[itr+1], gvn_lst[itr]
print("The above given list after sorted in waveform :")
# Loop from 0 to length of the given list using the for loop.
for itr in range(0, len(gvn_lst)):
# Inside the loop, print the given list of iterator values to sort the list in a waveform.
print(gvn_lst[itr], end=' ')


Output:

The above given list after sorted in waveform :
2 1 5 4 7 6 9

Method #2: Using For loop (User Input)

Approach:

• Give the list as user input using list(),map(),input(),and split() functions.
• Store it in a variable.
• Sort the above-given list using the sort() function.
• Calculate the length of the given list using the len() function and store it in another variable.
• Loop from 0 to length of the given list with a step size of 2 using the for loop.
• Assign a given list of (iterator +1) values to the given list of iterator and a given list of the iterator to the given list of iterator+1.
• Loop from 0 to length of the given list using the for loop.
• Inside the loop, print the given list of iterator values to sort the list in a waveform.
• The Exit of the Program.

Below is the implementation:

# Give the list as user input using list(),map(),input(),and split() functions.
#Store it in a variable.
gvn_lst = list(map(int, input(
'Enter some random List Elements separated by spaces = ').split()))
# Sort the above-given list using the sort() function.
gvn_lst.sort()
# Calculate the length of the given list using the len() function and
# store it in another variable.
len_lst = len(gvn_lst)
# Loop from 0 to length of the given list with a step size of 2 using the for loop.
for itr in range(0, len_lst-1, 2):
# Assign a given list of (iterator +1) values to the given list of iterator and
# a given list of the iterator to the given list of iterator+1.
gvn_lst[itr], gvn_lst[itr+1] = gvn_lst[itr+1], gvn_lst[itr]
print("The above given list after sorted in waveform :")
# Loop from 0 to length of the given list using the for loop.
for itr in range(0, len(gvn_lst)):
# Inside the loop, print the given list of iterator values to sort the list in a waveform.
print(gvn_lst[itr], end=' ')


Output:

Enter some random List Elements separated by spaces = 15 16 17 1 2 3
The above given list after sorted in waveform :
2 1 15 3 17 16

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