feat: implemented solution to LeetCode 3146 using a hashmap

Author: XavierCruz5106

lesson_13/maps_java/maps_app/src/main/java/com/codedifferently/lesson13/Lesson13.java

@@ -1,12 +1,26 @@
 package com.codedifferently.lesson13;
 
+import java.util.HashMap;
+
 public class Lesson13 {
 
   /**
    * Provide the solution to LeetCode 3146 here:
    * https://leetcode.com/problems/permutation-difference-between-two-strings
    */
   public int findPermutationDifference(String s, String t) {
-    return 0;
+    HashMap<Character, Integer> map = new HashMap<>();
+
+        for(int i = 0; i<t.length(); i++){
+            map.put(t.charAt(i), i);
+        }
+
+        int difference = 0;
+        for(int i = 0; i<s.length(); i++) {
+            int idx = map.get(s.charAt(i));
+            difference += Math.abs(i - idx);
+        }
+
+        return difference;
   }
 }