Update 268-missing-number.js

Author: everthis

268-missing-number.js

@@ -1,3 +1,16 @@
+/**
+ * @param {number[]} nums
+ * @return {number}
+ */
+const missingNumber = function(nums) {
+  const n = nums.length
+  let xor =  0 ^ nums[0]
+  for(let i = 1; i < n; i++) xor = xor ^ i ^ nums[i]
+  return xor ^ n
+};
+
+// another
+
 /**
  * @param {number[]} nums
  * @return {number}