feat: implementation of lesson13 using HashMap by Yemi

Author: jimoye244

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

@@ -1,13 +1,19 @@
 package com.codedifferently.lesson13;
 
+import java.util.HashMap;
+
 public class Lesson13 {
   public int findPermutationDifference(String s, String t) {
+    var indexMap = new HashMap<Character, Integer>();
+    for (int i = 0; i < t.length(); i++) {
+        indexMap.put(t.charAt(i), i);
+    }
+
     int result = 0;
-    int strLen = s.length();
-    for (int i = 0; i < strLen; i++) {
-      char ch = s.charAt(i);
-      result = result + (Math.abs(s.indexOf(ch) - t.indexOf(ch)));
+    for (int i = 0; i < s.length(); i++) {
+        // Default to -1 if char not found
+        result += Math.abs(i - indexMap.getOrDefault(s.charAt(i), -1)); 
     }
     return result;
-  }
+ }
 }