diff --git a/lesson_13/maps_java/maps_app/src/main/java/com/codedifferently/lesson13/Lesson13.java b/lesson_13/maps_java/maps_app/src/main/java/com/codedifferently/lesson13/Lesson13.java
index 0c981abbf..dc424ebf8 100644
--- a/lesson_13/maps_java/maps_app/src/main/java/com/codedifferently/lesson13/Lesson13.java
+++ b/lesson_13/maps_java/maps_app/src/main/java/com/codedifferently/lesson13/Lesson13.java
@@ -1,5 +1,7 @@
 package com.codedifferently.lesson13;
 
+import java.util.HashMap;
+
 public class Lesson13 {
 
   /**
@@ -7,6 +9,22 @@ public class Lesson13 {
    * https://leetcode.com/problems/permutation-difference-between-two-strings
    */
   public int findPermutationDifference(String s, String t) {
-    return 0;
+
+    HashMap<Character, Integer> indexFinder = new HashMap<>();
+
+    for (int i = 0; i < s.length(); i++) {
+      char character = s.charAt(i);
+      indexFinder.put(character, i);
+    }
+
+    int sum = 0;
+
+    for (int i = 0; i < t.length(); i++) {
+      char character = t.charAt(i);
+      int value = indexFinder.get(character);
+      sum += Math.abs(value - i);
+    }
+
+    return sum;
   }
 }