Program to check whether list is alternating increase and decrease or not in Python

Suppose we have a list of numbers called nums. We have to check whether the list alternates starting from strictly increasing then strictly decreasing and then strictly increasing and so on. And also if the list is only strictly increasing, it will be valid.

So, if the input is like nums = [2, 4, 8, 7, 5, 1, 5, 7, 2, 1], then the output will be True, because [2,4,8] are increasing, then [7,5,1] is decreasing, then again [5,7] is increasing and [2,1] is decreasing.

To solve this, we will follow these steps −

• if nums[1] <= nums[0], then
  • return False
• for i in range 0 to size of nums, do
  • if i - 1 >= 0, then
    • if nums[i] is same as nums[i - 1], then
      • return False
• return True

Example

Let us see the following implementation to get better understanding −

def solve(nums):
   if nums[1] <= nums[0]:
      return False
   for i in range(len(nums)):
      if i - 1 >= 0:
         if nums[i] == nums[i - 1]:
            return False

   return True

nums = [2, 4, 8, 7, 5, 1, 5, 7, 2, 1]
print(solve(nums))

Input

[2, 4, 8, 7, 5, 1, 5, 7, 2, 1]

Output

True

Arnab Chakraborty

Published on 14-Oct-2021 10:14:55

• Related Questions & Answers
• Python program to check whether a list is empty or not?
• C# program to check whether a list is empty or not
• Program to check whether given list is in valid state or not in Python
• Program to check whether given graph is bipartite or not in Python
• Python program to check whether a given string is Heterogram or not
• Program to check whether the sentence is pangram or not using Python
• Program to check whether given matrix is Toeplitz Matrix or not in Python
• Program to check whether a binary tree is complete or not in Python
• Program to check whether a binary tree is BST or not in Python
• Program to check whether given number is Narcissistic number or not in Python
• Program to check whether given tree is symmetric tree or not in Python
• Program to check whether parentheses are balanced or not in Python
• Program to check whether list of points form a straight line or not in Python
• Program to check whether list is strictly increasing or strictly decreasing in Python
• Program to check whether one value is present in BST or not in Python