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..a6eac947 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 +9,15 @@ public class Lesson13 {
    * https://leetcode.com/problems/permutation-difference-between-two-strings
    */
   public int findPermutationDifference(String s, String t) {
-    return 0;
+    var sIndexByChar = new HashMap<Character, Integer>();
+    int permDiff = 0;
+    for (int i = 0; i < s.length(); i++) {
+      sIndexByChar.put(s.charAt(i), i);
+    }
+    for (char key : sIndexByChar.keySet()) {
+      int indexInT = t.indexOf(Character.toString(key));
+      permDiff += Math.abs(s.indexOf(key) - indexInT);
+    }
+    return permDiff;
   }
 }
diff --git a/lesson_13/maps_ts/src/lesson13.ts b/lesson_13/maps_ts/src/lesson13.ts
index 5207487e..6ee168f9 100644
--- a/lesson_13/maps_ts/src/lesson13.ts
+++ b/lesson_13/maps_ts/src/lesson13.ts
@@ -3,5 +3,14 @@
  * https://leetcode.com/problems/permutation-difference-between-two-strings
  */
 export function findPermutationDifference(s: string, t: string): number {
-  return 0;
+  const sIndexByChar = new Map<string, number>();
+  let permDiff = 0;
+  for (let i = 0; i < s.length; i++) {
+    sIndexByChar.set(s.charAt(i), i);
+  }
+  for (const key of sIndexByChar.keys()) {
+    const indexInT = t.indexOf(key);
+    permDiff += Math.abs(s.indexOf(key) - indexInT);
+  }
+  return permDiff;
 }