feat: added lesson13.ts extra credit for Chelsea

Author: Cogbonnia

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

@@ -16,6 +16,7 @@ public int findPermutationDifference(String s, String t) {
     }
 
     int permutationDifference = 0;
+     
     for (int i = 0; i < t.length(); i++) {
       char ch = t.charAt(i);
       int indexInS = indexMap.get(ch);

lesson_13/maps_ts/package-lock.json

@@ -22,7 +22,7 @@
     "@nestjs/testing": "^10.4.4",
     "@stylistic/eslint-plugin": "^2.8.0",
     "@types/eslint__js": "^8.42.3",
-    "@types/jest": "^29.5.13",
+    "@types/jest": "^29.5.14",
     "@types/node": "20.12.7",
     "copyfiles": "^2.4.1",
     "eslint": "^9.11.1",
@@ -34,6 +34,5 @@
     "tsc-watch": "^6.2.0",
     "typescript": "^5.6.2",
     "typescript-eslint": "^8.7.0"
-  },
-  "dependencies": {}
+  }
 }

lesson_13/maps_ts/package.json

@@ -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;
 }