Add solution #268

Author: JoshCrozier

README.md

@@ -28,6 +28,7 @@
 226|[Invert Binary Tree](./0226-invert-binary-tree.js)|Easy|
 263|[Ugly Number](./0263-ugly-number.js)|Easy|
 264|[Ugly Number II](./0264-ugly-number-ii.js)|Medium|
+268|[Missing Number](./0268-missing-number.js)|Easy|
 283|[Move Zeroes](./0283-move-zeroes.js)|Easy|
 345|[Reverse Vowels of a String](./0345-reverse-vowels-of-a-string.js)|Easy|
 347|[Top K Frequent Elements](./0347-top-k-frequent-elements.js)|Medium|

solutions/0268-missing-number.js

@@ -0,0 +1,25 @@
+/**
+ * 268. Missing Number
+ * https://leetcode.com/problems/missing-number/
+ * Difficulty: Easy
+ *
+ * Given an array `nums` containing `n` distinct numbers in the range `[0, n]`,
+ * return the only number in the range that is missing from the array.
+ *
+ * Follow up: Could you implement a solution using only `O(1)` extra space
+ * complexity and `O(n)` runtime complexity?
+ */
+
+/**
+ * @param {number[]} nums
+ * @return {number}
+ */
+var missingNumber = function(nums) {
+  let result = 0;
+
+  for (let i = 0; i < nums.length; i++) {
+    result += i + 1 - nums[i];
+  }
+
+  return result;
+};