Here is my c++ solution, you can watch the explanation here : https://youtu.be/B4pZbX0VzzU

#include <bits/stdc++.h>

using namespace std;

int main()
{
    string fstr, sstr;
    cin >> fstr; cin >> sstr;
    vector<int>fsc(26,0), ssc(26,0);
    int i, result = 0;
    for(i = 0; i < fstr.size(); i++) fsc[fstr[i] - 'a']++;
    for(i = 0; i < sstr.size(); i++) ssc[sstr[i] - 'a']++;
    for(i = 0; i < 26; i++) result += abs(fsc[i] - ssc[i]);
    cout << result << endl;
    return 0;
}

int makingAnagrams(string s1, string s2) { int arr[26] = {0}; for(int i = 0 ; i < s1.size(); i++) { arr[s1[i] - 'a']++; }

for(int i = 0 ; i < s2.size(); i++)
{
    arr[s2[i] - 'a']--;
}
int count = 0;
for(int i = 0; i < 26; i++)
{
   if(arr[i] > 0)
   {
       count = count + arr[i]; 
   } 
   else if(arr[i] < 0)
   {
       count = count + abs(arr[i]);
   }
}
return count;

}

return 0;

}

int makingAnagrams(string s1, string s2) {

        unordered_map<char, int> mymap1;
        int i = 0, remove = 0;

        while(i < s1.size())
        {  
                mymap1[s1[i]] += 1;          
                i++;
        }

        i = 0;

        while(i < s2.size())
        {             
                mymap1[s2[i]] -= 1;  
                i++;
        }

        auto it = mymap1.begin();

        while(it != mymap1.end()) {

                remove += abs(it->second);
                it++;
        }

        return remove;
}

Using Python3 defaultdict

def makingAnagrams(s1, s2):
    d=defaultdict(int)
    for c in s1:
        d[c]+=1
    for c in s2:
        d[c]-=1
    return sum(abs(v) for k,v in d.items())

C++:

int makingAnagrams(string s1, string s2) {

    for(int i = 0; i < s1.size(); i++)
        for(int j = 0; j < s2.size(); j++)
            if(s1[i] == s2[j]){
                
                s1.erase(i, 1);
                s2.erase(j, 1);
                i--;
                j--;
            }

    return s1.size() + s2.size();
}