268. Missing Number

nums holds n distinct numbers from the range [0, n]. Return the only number in that range that is missing.

XOR all indices 0..n and all values. Every present number cancels with its index (x ^ x = 0), leaving only the missing one.

1function missingNumber(nums: number[]): number {
2  let x = nums.length;
3  for (let i = 0; i < nums.length; i++) {
4    x ^= i ^ nums[i];
5  }
6  return x;
7}