Missing Number | Problems

You get an array nums of length n. It contains n distinct integers, each in the range [0, n] inclusive. Exactly one integer in that range is missing from the array. Find and return that missing number.

The full set should be {0, 1, …, n}; the array lists n of them.

Example 1

Input: nums = [3, 0, 1]
Output: 2

Example 2

Input: nums = [0, 1]
Output: 2 (numbers present are 0 and 1; n = 2, so missing is 2)

Example 3

Input: nums = [9, 6, 4, 2, 3, 5, 7, 0, 1]
Output: 8

Constraints

n == nums.length
1 <= n <= 10^4
0 <= nums[i] <= n
All values in nums are distinct

Sample Input

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Sample Output

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Constraints

n == nums.length
1 <= n <= 10^4
0 <= nums[i] <= n
All numbers are unique

Test Cases

Case 1

Args: [[3,0,1]] Expected: 2

Case 2

Args: [[0,1]] Expected: 2

Case 3

Args: [[9,6,4,2,3,5,7,0,1]] Expected: 8

Topics

Matrix BFS DFS

XOR or Math

function missingNumber(nums) {
  const n = nums.length;
  return n * (n + 1) / 2 - nums.reduce((a, b) => a + b, 0);
}

Time: O(n) | Space: O(1)

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