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 0c981abb..e4873c38 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 +9,18 @@ public class Lesson13 {
    * https://leetcode.com/problems/permutation-difference-between-two-strings
    */
   public int findPermutationDifference(String s, String t) {
-    return 0;
+    var stringS = new HashMap<Character, Integer>();
+
+    int totalDifference = 0;
+
+    for (int sIndex = 0; sIndex < s.length(); sIndex++) {
+      stringS.put(s.charAt(sIndex), sIndex);
+    }
+    for (int tIndex = 0; tIndex < t.length(); tIndex++) {
+      int countIndexS = stringS.put(t.charAt(tIndex), tIndex);
+
+      totalDifference += Math.abs(countIndexS - tIndex);
+    }
+    return totalDifference;
   }
 }