Least number of manipulations needed to ensure two strings have identical characters

Given two strings return the value of least number of manipulations needed to ensure both strings have identical characters, i.e., both string become anagram of each other.

Examples: 

Input : s1 = "aab"
 s2 = "aba" 
Output : 2
Explanation : string 1 contains 2 a's and 1 b, 
also string 2 contains same characters

Input : s1 = "abc"
 s2 = "cdd"
Output : 2
Explanation : string 1 contains 1 a, 1 b, 1 c
while string 2 contains 1 c and 2 d's
so there are 2 different characters

Question Source : Yatra.com Interview Experience | Set 7

The idea is to create a extra count array for both the strings separately and then count the difference in characters. 

Implementation:

2