#333 Missing Number

Given an array nums containing n distinct numbers in range [0, n], return the only number in the range that is missing.

Rules:

• Array contains n distinct numbers
• Numbers are in range [0, n]
• Exactly one number is missing
• Try to use O(1) extra space
• Try to achieve O(n) runtime

Constraints:

• 1 ≤ nums.length ≤ 1000
• All numbers are unique
• Numbers are in range [0, n]

Examples:

// Example 1:
console.log(missingNumber([1, 2, 3]));
// Output: 0
// Explanation: Range is [0,3], 0 is missing

// Example 2:
console.log(missingNumber([0, 2]));
// Output: 1
// Explanation: Range is [0,2], 1 is missing