array_transformation.py

# https://leetcode.com/problems/array-transformation/description/
# 1243. Array Transformation

# Given an initial array arr, every day you produce a new array using the array of the previous day.
# On the i-th day, you do the following operations on the array of day i-1 to produce the array of day i:
# If an element is smaller than both its left neighbor and its right neighbor, then this element is incremented.
# If an element is bigger than both its left neighbor and its right neighbor, then this element is decremented.
# The first and last elements never change.
# After some days, the array does not change. Return that final array.

# Example 1:
# Input: arr = [6,2,3,4]
# Output: [6,3,3,4]
# Explanation: 
# On the first day, the array is changed from [6,2,3,4] to [6,3,3,4].
# No more operations can be done to this array.

# Example 2:
# Input: arr = [1,6,3,4,3,5]
# Output: [1,4,4,4,4,5]
# Explanation: 
# On the first day, the array is changed from [1,6,3,4,3,5] to [1,5,4,3,4,5].
# On the second day, the array is changed from [1,5,4,3,4,5] to [1,4,4,4,4,5].
# No more operations can be done to this array.

# Constraints:
# 3 <= arr.length <= 100
# 1 <= arr[i] <= 100

from typing import List

class Solution:
    def transformArray(self, arr: List[int]) -> List[int]:
        ''' Array Transformation '''
        transformable = True
        while transformable:
            transformable = False
            t = arr[:]
            for i in range(1, len(t) - 1):
                if t[i] > t[i - 1] and t[i] > t[i + 1]:
                    arr[i] -= 1
                    transformable = True
                if t[i] < t[i - 1] and t[i] < t[i + 1]:
                    arr[i] += 1
                    transformable = True
        return arr


print(Solution().transformArray([6,2,3,4]))
# Output: [6,3,3,4]
print(Solution().transformArray([1,6,3,4,3,5]))
# Output: [1,4,4,4,4,5]
print(Solution().transformArray([1,5]))
# Output: [1,5]