✔️ add solution for Dynamic Array problem.

Author: modavidc

Diff for: README.md

@@ -34,6 +34,7 @@
 |:---------------------------:|:----------------------------------------------------------------------------------------------------------------------------:|:------:|:----------:|:-------------------------------------------------------------------------------------------------:|
 |        Arrays               | [Arrays - DS](https://www.hackerrank.com/challenges/arrays-ds)                                                               |   10   |    Easy    | [solution.js](arrays/arrays-ds.js)                                                                |
 |        Arrays               | [Left Rotation](https://www.hackerrank.com/challenges/array-left-rotation)                                                   |   20   |    Easy    | [solution.js](arrays/left-rotation.js)                                                            |
+|        Arrays               | [Left Rotation](https://www.hackerrank.com/challenges/dynamic-array)                                                         |   15   |    Easy    | [solution.js](arrays/dynamic-array.js)                                                            |
 
 ## 👤 Author
 

Diff for: arrays/dynamic-array.js

@@ -0,0 +1,40 @@
+// Problem: https://www.hackerrank.com/challenges/dynamic-array/problem
+
+function dynamicArray(n, queries) {
+    // Declare a 2-dimensional array, *arr*, of *n* empty arrays. All arrays are zero indexed.
+    let arr = [];
+    for (let i = 0; i < n; i++) {
+        arr.push([]);
+    }
+    // Declare an integer, lastAnswer, and initialize it to 0.
+    let lastAnswer = 0;
+    // Declare an array for store the new values of lastAnswer
+    let lastAnswers = [];
+
+    for(let j=0; j<queries.length; j++) {
+        let queryType = queries[j][0];
+        let x = queries[j][1];
+        let y = queries[j][2];
+        
+        let idx = ((x ^ lastAnswer) % n);
+        
+        // Query: 1 x y
+        if( queryType == '1') {
+            arr[idx].push(y);
+        } 
+        // Query: 2 x y
+        else {
+            lastAnswer = arr[idx][ y % arr[idx].length];
+            lastAnswers.push(lastAnswer);
+        }
+    }
+
+    return lastAnswers;
+}
+
+// test 1
+let t1Size = 2;
+let t1Array = new Array(new Array(1, 0, 5), new Array(1, 1, 7), new Array(1, 0, 3), new Array(2, 1, 0 ), new Array(2, 1, 1 ));
+
+let t1Result = dynamicArray(t1Size, t1Array);
+console.log(t1Result);