Transform String

//{ Driver Code Starts
#include <bits/stdc++.h>
#include <unordered_map>
using namespace std;


// } Driver Code Ends
class Solution
{
    public:
    int transform (string A, string B)
    {
        //code here.
        int n=A.length();
        int m=B.length();
        if(n!=m)
        {
            return -1;
        }
        else
        {
            unordered_map<char,int> mp;

            for(int i=0;i<n;i++)
            {
                mp[A[i]]++;
            }
            for(int i=0;i<n;i++)
            {
                mp[B[i]]--;
            }

            for(auto u:mp)
            {
                if(u.second!=0)
                {
                    return -1;
                }
            }

             int i=n-1,j=m-1;
               int c=0;
               while(i>=0 && j>=0)
               {
                   if(A[i]==B[j])
                   {
                       i--;
                       j--;
                   }
                   else
                   {
                       c++;
                       i--;
                   }
               }
               return c;

        }
    }
};


//{ Driver Code Starts.

int main ()
{
    int t; cin >> t;
    while (t--)
    {
        string A, B;
        cin >> A >> B;
        Solution ob;
        cout <<ob.transform (A, B) << endl;
    }
}
// } Driver Code Ends