Program to find the percentage of difference between two numbers

Given two numbers a and b, where 'b' is incremented or decremented by some percentage of 'a'. The task is to find out that percentage.

Examples: 

Input: a = 20, b = 25
Output: 25% 
Difference between 20 and 25 is 5, 
which is 25 % of 20.
(+ve sign indicate increment)

Input: a = 25, b = 20
Output: -20% 
( -ve sign indicate decrement)

Formula to calculate percentage: 

(Percentage2 - Percentage1) * 100 / (Percentage1) 
  

25%

Time Complexity: O(1)
Auxiliary Space: O(1)