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..5847508e6 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 +1,8 @@
 package com.codedifferently.lesson13;
 
+import java.util.HashMap;
+import java.util.Map;
+
 public class Lesson13 {
 
   /**
@@ -7,6 +10,18 @@ public class Lesson13 {
    * https://leetcode.com/problems/permutation-difference-between-two-strings
    */
   public int findPermutationDifference(String s, String t) {
-    return 0;
+    Map<Character, Integer> indexMap = new HashMap<>();
+    for (int i = 0; i < s.length(); i++) {
+      indexMap.put(s.charAt(i), i);
+    }
+
+    int permutationDifference = 0;
+
+    for (int i = 0; i < t.length(); i++) {
+      char ch = t.charAt(i);
+      int indexInS = indexMap.get(ch);
+      permutationDifference += Math.abs(indexInS - i);
+    }
+    return permutationDifference;
   }
 }
diff --git a/lesson_13/maps_ts/src/lesson13.ts b/lesson_13/maps_ts/src/lesson13.ts
index 5207487e2..09771647e 100644
--- a/lesson_13/maps_ts/src/lesson13.ts
+++ b/lesson_13/maps_ts/src/lesson13.ts
@@ -3,5 +3,21 @@
  * https://leetcode.com/problems/permutation-difference-between-two-strings
  */
 export function findPermutationDifference(s: string, t: string): number {
-  return 0;
+  const indexMap = new Map<string, number>();
+
+  for (let i = 0; i < s.length; i++) {
+    indexMap.set(s[i], i);
+  }
+
+  let permutationDifference = 0;
+
+  for (let i = 0; i < t.length; i++) {
+    const ch = t[i];
+    const indexInS = indexMap.get(ch);
+    if (indexInS !== undefined) {
+      permutationDifference += Math.abs(indexInS - i);
+    }
+  }
+
+  return permutationDifference;
 }