feat: adds lesson 13 permutation difference solution in javascript and java

Author: karensprojects22

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

@@ -1,12 +1,33 @@
 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;
+    // initializing the permuation difference between the characters 
+    int difference = 0;
+
+    // creating a hashmap to store the index of each character in s - the key value pair
+    // the key is the character and the value is the index
+    HashMap<Character, Integer> characterPosition = new HashMap<>();
+
+    // iterates through character in s with i as index
+    for (int i = 0; i < s.length(); i++) {
+      // returns the map of character at a given index 
+      characterPosition.put(s.charAt(i), i);
+    }
+    
+    // calcualting permutation difference
+    for (int i = 0; i < t.length(); i++) {
+      //using a built in function - math.abs to calculate the difference in character index
+      // index of character in string s - index of character in string i
+        difference += Math.abs(i - characterPosition.get(t.charAt(i)));
+    }
+    return difference;
   }
 }

lesson_13/maps_ts/src/lesson13.ts

@@ -3,7 +3,7 @@
  * https://leetcode.com/problems/permutation-difference-between-two-strings
  */
 export function findPermutationDifference(s: string, t: string): number {
-  // used chat gpt for this solution implementation
+  // used chat gpt for this extra credit solution implementation
 
   // variable difference keeps track of absolute difference between character index
   let difference = 0;