add two drafts

Author: rishabh1403

301-400/344-reverse-string.js

@@ -0,0 +1,12 @@
+var reverseString = function (s) {
+  let left = 0, right = s.length - 1;
+
+  while (left < right) {
+    const temp = s[left];
+    s[left] = s[right];
+    s[right] = temp;
+
+    left++;
+    right--;
+  }
+};

501-600/509-fibonacci-number.js

@@ -0,0 +1,26 @@
+
+
+// Recursive solution
+var fib = function (N) {
+  if (N === 0 || N === 1) return N;
+
+  return fib(N - 1) + fib(N - 2);
+
+};
+
+// Iterative solution
+var fib = function (N) {
+  if (N === 0 || N === 1) return N;
+
+  let first = 0, second = 1;
+  let sum = first + second;
+
+  for (let i = 2; i < N; i++) {
+    first = second;
+    second = sum;
+
+    sum = first + second;
+  }
+
+  return sum
+};