$($a$)$ Write a function that takes a string and creates another string substituting each character of the original string with the character immediately before it$.$

Sample input: "all is well"

Output: $"$zkk hr vdkk$"$

$($b$)$ Write a function that takes a List of integers and returns True if the absolute difference between each adjacent pair of elements strictly increases, Otherwise return False.

Sample input: $L=[3,4,7,11,17]$

Output: True